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56 Vic, B'Ville 200 MPH Club Member, So Cal.

We bought a "Champion" radiator for our 56 Ranch Wagon and are pretty happy with it. Dimensionally, it fit perfectly. If you are running an automatic though, be prepared to bend your transmission cooling lines a bit because the bottom tank on the radiator is configured a little differently than stock which changes the angle of the fittings on the bottom tank. Trying to bend the steel lines to make them fit is kind of a PAIN!

Rono

  Ron Lane,  Meridian, ID

my 57ranchero has the original type rad(,cleaned ,180 stat original bypass hose unrestricted) stock pump pulley.temp guage is new location a the front of intake..i ran in heaven trafic all summer which was our hotest in years. no heating issues. i use anty freeze all year as anty freeze has better heat exchange than water. myn is 292/ 040 bore with 4v,and std trans.  years ago a buddy had a 55 272 fordamatic,in traffic he always shifted to n that unloaded engine and helped cool trans(air cooled torqe.)
 must admit that those in ca in the summer with traffic are in a different world than i am.

My car has a 5 blade fan that has a Ford part number on it. Not sure what it is off but it pulls lots of air at idle and my pump pulley is larger than the crank pulley. It has large flex blades with an enormous pitch that flatten at higher revs so less power robbing. Other than the fan all is original, no blocked bypass, copper and brass radiator, 180 thermostat. The only time I ever see the temp creep up is when stuck in traffic on 100F or higher days, but it has never boiled, and I'm sure a smaller pump pulley would probably cure that.
I recall on this sight a link from another car group that did exhaustive testing and came to the conclusion that stationary overheating if there are no mechanical problems was usually the result of not enough air flow.
From the original question, in my case the YBlock is the best of any car I've had to get to running temperature quickly.
I find easiest way to check bottom hose is just to squeeze it when cold and you can quickly feel if the wire is still all intact.

It sounds to me like the engine has a vacuum leak  - that gets bigger AFTER a period of running. Is this engine still running a factory initial time setting - with a Load-O-Matic distributor? 
Lose vacuum - Idle speeds up - Spark retards.

 
 Steve Metzger       Tucson, Arizona

Man that fan really does look like it would move a lot of air Ian57!

So if I wanted to check the block for blockages inside the coolant channels, how hard are the freeze-plugs to pull out and get in there? Are they difficult to get back in again? And do you run the risk of causing leaks from those things if you mess with them?

Found this one for a 66' Mustang offered at O'Rileys... is this what you got?

I remember that flex fans were prone for the blades flying off. One customer of the gas station I worked at had a nasty slice in his hood from a blade that flew off. The dealer replaced it with a clutch fan. They were deemed dangerous and we were told not to stand next to the fan with the engine running.

1/2 Dude - how does the vacuum look when you are up at the "overheat" situation?

Flex fans have a problem, especially with truck applications - where you are climbing a long grade ( I was living in the mountains at the time) at elevated rpm (lower gear). Fan flattens out - moves less air at just the wrong time......... lots of load lots of revs and reduced airflow.
Conventional six blade, direct drive is a good choice - the one I have on the car now is an aluminum 7 blade off an older Pontiac. I think Ford was using a five blade on the air-conditioned cars of that era.

 
 Steve Metzger       Tucson, Arizona