.Is this old "Y"block a 54 or 55 ? or what?

[55blacktie]

I think it's already been stated that "9425" will be on all of the intake manifolds. 9425A is a small-base intake manifold for Holley 8000 Teapot carburetors and was used in 1955 and 1956. It's the OEM manifold for my 1955 T-bird; it's not exclusive to 56. My car was manufactured Jan 20, 1955.

 

[55blacktie]

Ooops! Would two Teapots equal 8000? The 4-bbl. Teapot is a Holley 4000.

 

[dmsfrr]

Sounds like it is a '56, 292 Y-block, but then it should have had the dual vacuum advance distributor for the 4-bbl intake, right?

Yes, the dual canister '56 (Loadomatic) distributor normally goes on the '56 4 bbl engines.
It's my understanding the 2 bbl '56 engines used a single sided canister.

 

[dmsfrr]

I think it's already been stated that "9425" will be on all of the intake manifolds. 9425A is a small-base intake manifold for Holley 8000 Teapot carburetors and was used in 1955 and 1956. It's the OEM manifold for my 1955 T-bird; it's not exclusive to 56. ...

55blacktie,
If you have a '56 ECZ-A intake on the engine in a '55 T-Bird, someone swapped it on there in place of the original. You could double check the engine block casting number too.
http://ford-y-block.com/Block%20identification.htm

The original 4bbl intake manif on a '55 T-Bird is an ECB-9425-B .(from page 34 #17 CTCI restoration manual) Example photos below...
They have the choke thermostat below the carburetor, mounted to a flat spot on the exhaust crossover.