1978 Trans Am - Help Needed

[TStick]

I recently bought a 1978 T/A sport coupe.

Originally, it came with the 6.6l 400.

I was tearing it down for a rebuild but ran into some issues.

The engine is not a 400.

Heads are 4X, with a secondary stamp of 1H, and the front edge has #206318 YY. Ang G203

Block: #485428

So if I am deciding this right, it's a 1973 455CI with July 20 1973 heads.

I want to order the correct things. VIN# 2W87Z8L169478

 

[TStick]

Update: Pontiac shows it as a 1974 455 block code YY, 485428 4bbl HEI,

I still need GM gearheads to validate before ordering.

I am a Mopar guy, but I couldn't pass up the deal and opportunity to make a Bandit clone; I already have a donor roof section.