Yes the distributor does have weights and springs so at least 1957 and there is no vacuum at idle and almost no vacuum at full throttle. Cruising at 2000 rpm the gauge says between 15 and 20 inches of vacuum

Your vacuum reading (ported) is correct. When you open the throttle blades the manifold vacuum drops.

Are you having some sort of performance problem?

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Sorry I now see my carburetor pictures showed the old 1956 distributor , these are current pictures of what I was told is a 1957 distributor 

1956 F100 272 4 speed
Northern California

Actually it drives really nice, no pinging, quick throttle response and smooth idle

1956 F100 272 4 speed
Northern California

I will try to make a video of the vacuum gauge responding to the gas pedal while driving. The gauge is at zero at idle and almost down to zero at full throttle.
Also thanks for all the input

1956 F100 272 4 speed
Northern California

You have the 1957/59 DUAL ADVANCE DIST w the SINGLE BREAKER PLATE (it advances/rotates while riding on ball bearings). The vacuum advance canister is correct also. You should be good to go.

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1956 F100 272 4 speed
Northern California

You've got it brother!

No shake, rattle or roll, no tip-in hesitation and she sounds perfect to me.

Someone had to modify the carb at some point for the 57/ DUAL ADV DIST.

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Thanks,  I was wondering if the carb could have been modified, from what I understand it acts more like ported vacuum and not venturi vacuum 

1956 F100 272 4 speed
Northern California

You do have ported vacuum signal now. Venturi vacuum was one source of vacuum signal used on the older/previous LOAD-O-MATIC SYSTEM.

You are OK (IMO).

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It sounds like you're actively trying to find something to worry about, ha ha. This should not be difficult these days. I'm prone to this at times. Proper setup of the vacuum advance is critical, I think, for an all around good smooth and cool running "street" engine. Detroit thought so too, they incorporated it practically from the beginning. But you might need to back up a bit.

It's important to tune the ignition timing in sequence or correct order. The way to do that, is disconnect and plug the vacuum advance. Forget, for the moment, that it even exists. (Remember hot rodders and drag racers don't even have a vacuum advance on their motors, because it isn't doing anything under full throttle).

Using your timing light, first ensure that the mechanical or centrifugal advance is doing what it's supposed to do, and, just as importantly, when it's supposed to be doing it, from idle to wide open throttle, and everything in between. Cruise level RPM.

In a stock Y Block wide open throttle might be something like 34 to 36 degrees (maybe more) of ignition advance, and importantly all before 3000 RPM. This can be achieved by adjusting the internal distributor combination of slots and springs. This might take a few test drives with vacuum advance disabled.

In effect what you're doing is using your engine as a distributor test machine. Most Y Blocks seem to like plenty of initial advance, more than the factory spec of 3 to 6 degrees. Somewhere around 12 degrees or so. This setting however might require some adjustment internally to limit or prevent excessive "total" advance.

Anyway once you optomize or "curve" your mechanical ignition advance, then you can re-connect the vacuum canister and play with that. The shop manual lists all the specifications in the Ignition section, what it should be at various RPM or vacuum levels - but keep in mind those published numbers are based on distributor degrees, not crankshaft degrees. They will be exactly double at the crankshaft. This is good place to start.

Yes it's true, doing all of this stuff can be tedious without a distributor machine, but it's worth taking the time if you want a good, sharp tune.