Anyway this is what he says it is: " its a brand new,gm 496,8.1 L,4 bolt block and gm crankshaft for the same.block casting number is 12558110, the crank has the number 721 cast onto it,on one throw,179 cast into another,and the letters HS 340 stamped ,not cast,onto another." Is this the base for a good build or am I better off with a 454 and starting with it? If there is a 496 block, why would you wanna use the 454 to get to a ci that exists already?