I tried Mortec and didnt get much. I bought a 454 from RyanB. and just got to checking the casting numbers on it. As luck would have it the info on Mortec is very vague for the numbers I have. Particularly the stamped asembly code. Here they are: Assembly code on boss behind alternaor: CFS743209 Block casting # in rear where the bellhousing bolts up, driver side: 14015445 Next to that, still on driver side: GM 1 P ,then a symbol that looks like a playing piece for trivial pursuit, CFD Date code, pass side, where the bellhousing bolts up: 339 Behind the flexplate, driver side: M IV, 2, High Perf My heads: 14087487 Any info beyond what I was able to find on Mortec, which wasn't much, would be appreciated.