LIke the later FE engines, the "Thunderbird" valve cover markings are not too indicative of the engine components.

Specific to ’55-’57 Thunderbird engines would be:

1” spacer behind the water pump

Forward facing outlet on the thermostat housing

Tach drive on the distributor

Special mount that allows generator to be mounted further forward

Unique harmonic damper that has the pulleys much further forward.

Unique exhaust manifold on the drivers side

Rear sump oil pan (different than pickup and truck models)

This is all that comes to mind so anyone else add those items I missed.

The Birds had an inline glass fuel filter up near the carb, the pass cars had a glass filter under the fuel pump

The Birds had chrome 3 blade fans, the pass car fans were painted

The Birds had a road draft tube out of the valley cover down the right side of the engine near the starter, the pass cars had the road draft tube on the left side of the block.

The birds have a Timing Chain Cover like the truck ie long bolt bosses around the damper for the front steady rest but there are no tapped holes in the flats on top. The pass cars TCC's have no flatsor tapped holes on top and have short bolt bosses

If the engine isn't going in a T bird not too much of this matters,  In fact the specific T bird stuff, primarily the Harmonic balancer, the side steady rests, the distributor and the oil pan are worth a lot to the T bird people and not so much to the performance Y's guys unless they are running T birds.

Most origiinal '55's were 272's but there were also 292's in pass cars, ALL '55 birds were 292's