I'm considering pressurizing the rocker shafts on  my '55 292. I know there are at least a couple of methods, pinching off the shaft drain tubes appearing to be the easiest. My concern is about possibly starving some other part of the engine for oil. It looks like the output of the passenger side shaft goes to the timing chain. I don't know where the oil from the driver side tube goes, distributor/oil pump drive gear maybe...? I'm pretty sure a few guys here have done this so I'd like to know what method you used and the results before I pull the trigger. TIA for any advice.

Much has been written about this.  You will receive many replies.  I suggest you go to YouTube and check out the numerous videos on this subject.  I have done this a number of different ways myself.  Pinching off the tubes is one way.  You can block off the oil to the tubes in other ways as well.  I have never seen any noticeable adverse effects from these modifications on a street driven car.  Make sure you have enough oil flow to begin with.  In a Y-Block. the oil flows through small holes in the heads that can become easily blocked or restricted by sludge. 

When I built the engine in my TBrd, I handled this issue differently.   On this forum I learned that cutting the cam grove deeper increases oil flow to the heads. The oil grove in my new out of the box Isky cam had an .018" deep grove.  I put the cam in a lathe and cut the grove to .030".  I had so much oil in the top end, I decided to leave the oil tubes open.  Some people have had to restrict the oil flow after cutting the grove, in my case this wasn't necessary.  I have about 3,000 miles on my rebuild so far.  My valve adjustment and top end are as new.

Here is an older link related to this subject.
 
http://forums.y-blocksforever.com/FindPost10464.aspx
 
 
And here are some other discussions related to Y-Block oiling.
 
Center cam bearing
Grooving the center cam hole in the block
Oil Flow Diagram
Pressurized rocker shafts
Pressurized rocker shafts more
Pressurized timing chain oiling
Rocker arm overflow tubes Cons
Rocker arm overflow tubes Pros
Rocker arm overflow tube More Pros
Slotting the rocker shafts for improved oiling
Timing chain oil trough

Lorena, Texas (South of Waco)

Everything you always wanted to know about Y-Block Rockers, but were afraid to ask...  

first move is be sure the inside of the rocker shaft is clean, on higher milage the spill tubes plug up at opposite end of spill tubes..,those rockers and shaft suffer.
the tip from this form had some good info such as tap the end rocker stand, take a Allen screw grind a tapper this blocks the spill tube  drain and positions the assembly for easy inst.  my current ride has a 292 with the largend grove in cam and fullpresure to rockers, I installed early 289 umbrella seals on valve s
,I tried the umbrella 1/8 in. when running engine withe covers offsets of oil and all push rods spin which helps take oil into valley. the drain tubes on exhaust Sidadequate to handle  all the oil drain some to chain aria and dust drive. mine is in its 4th year, no issues and no increase ionic consumption. plus have not had to adjust the valves 3years. the rate of pushrods rotate says all is well  with cam and lifters

Leave it stock.

I found this on the FTE forum in a similar discussion:

Lets start with the FE. The FE also feeds the rocker shaft from the cam bearings but it uses 2 cam bearings (2 and 4) instead of just one cam bearing, The FE oiling system for the rockers/shaft also has a severe dog leg in it (both heads). But the big difference is it is pressurized.

Beyond that pressure is a function of flow. Input more flow than can be output and you build pressure.

Now where the issue arose with the Y block was 2 fold, the oils available in the era and the lack of a pressurized rocker shaft. We all know where the hottest part of an engine block is during operation, the cylinder head, this is also a factor in the Y blocks pugging up the rocker shaft oiling circuit.

As we all know the oils from back in the day had a much lower vapour point and in turn coking point temp wise than modern oils. And we all know how to raise the vapour point of a liquid, increase the pressure it is under.

The fact that the Y block had an unpressurized rocker shaft helped contribute to the coking and sludge build-up in the feed to the rocker shaft and within the rocker shaft itself. If the oil feeding the rocker shaft and the rocker shaft was/is pressurized the propensity for coking and sludge build-up in the oil passages and the rocker shaft will be greatly reduced. So pressurizing the rocker shaft will have an effect on the propensity of coking and sludge build-up.

The FE was built concurrently with the Y Blocks so both got used with the same oils in the era, yet it never suffered the same rocker wear issues of the Y block nor had near the issues of coking and sludge build-up in the rocker shafts, some of this was due to better oiling but a big part of it was due to the system being fully pressurized.

The Y Block stuck around till 1984 in South America and when they moved to the Phase 2 heads in the mid-late 60's (SBF style intake and exhaust port layout) the rocker shafts were fully pressurized and the overflow tube done away with.

Makes good sense to me. One thing I don't understand. Let's say someone simply pinches off the overflow tubes. Now the rocker shafts are pressurized, assuming that rocker shaft and rocker bore clearances are within clearance spec.

The oil that "leaks" past and through the rocker arms ultimately will travel along the head channel should and exit down through the very same drain holes anyway? I'm missing something surely, but that's not news.

Here are some more thoughts on the subject.
 
A major difference between the FE engines and the Ford Y is that the FE engines had hydraulic lifters while the Y had solids.  I am excluding the 406 and 427 Fords from this discussion.  With hydraulic lifters, the rockers are loaded against the shaft at all times which means there is no period of relaxation of the rocker to the shaft.  In this instance a pressurized rocker shaft will force oil in those locations that normally would not get it.  The Ford Y on the other hand does have that period of relaxation of the rockers to the shafts and simply relies on gravity to feed oil to the bottom of the shafts.  The overflow tubes do allow the shafts to stay full of oil thus eliminating air pockets while at the same time allows the flow of oil through the shafts to be increased thus carrying away the excess heat generated there.  Another plus to the overflow tubes is the right side of engine tube providing additional oil to the timing chain set that it would not receiver otherwise.  The oil trough on the early engines worked in tandem with the oil flow tubes to insure that the oil did indeed get on the chain.
 
As already mentioned, the root of the Ford Y top end oiling problems was with the use paraffin based oils of the time.  The Y was designed originally for the modern multi-weight oils that were introduced at the same time as the Y but not all owners saw fit to use those oils from the onset.  I do still see Ford Y engines with 300K miles with the overflow tubes still intact and these engines are still providng oil to the rockers.  These high mileage engines all run a good quality oil which is routinely changed.
 
A big fail point on engines being rebuilt now is with the softer than stock cam bearings that are being used.  The cam bearings end up wearing much quicker to the point that the groove in the center journal of the camshaft journal is pushed into the bearing thus either restricting the oil flow to the top or shutting it off completely.  Part of this accelerated wear comes from using valve spring pressures that are now much higher than stock.  Common fixes for this are using a center camshaft bearing that has a groove machined on the back side of it, cutting the groove in the center camshaft journal deeper, or machining a groove in the center cam bearing hole in the block that allows the three holes there to be connected thus eliminating the need for the groove in the camshaft.  A recent cam bearing for the Y from Engine Tech (made in South America) is made from a harder material and has thus far helped considerably in stopping the aforementioned problems associated with the softer cam bearing material.
  
For stock engines, I use the overflow tubes.  For performance applications where the valve spring pressures are increased, I will convert the shafts to a pressurized system.  All the Harland Sharp roller rocker arm assemblies I prepare are set up for pressurized oiling as these use bronze bushings within the rockers which are prone to galling if they starve for oil.

Lorena, Texas (South of Waco)

I would say that the cast rockers on hardened shafts are more likely to gall than bras . the people I deal with are not trying to make big power from the y blocks. the cost per hp in the old girls is to high.
 I strive to get best power posable,threw comen cents cost. the load on camshafts and galing  of rockers  and shafts  makes no cents. the oil draining threw the return holes is more than adequate to lube  tieing chain etc,as well lots of oil returns via push rods spinning. I do agree that modern oils work well as far as cloging rocker shafts, but do not come close to full pressure to all rockers and the spill that lubes the valve train.  I see no reason to increase spring pressure in valve train as if you are driving the vehicle on the street,these engines work best 5000 and under, and dollar pr hp best spent on good carbs and electronic ignition along with good exhaust, and hear in the coast of bc heat riser and elect. choke is a must.  I am sure to get bad press for my opinion but we Canadians know we are looked at as less wise than our us friends. but the population  of y Blocks and  high cost of parts made us creative