[GMH454]

Can you please put up all the numbers. If the 512 is the last 3 digits then this would be the first of the blocks cast for the 454. They were introduced after the 270 and in late 1968 although they may not have first been dropped in cars till early 1969. The four bolts by that time had a back log and sat on the shelves for quite a time before installation. Can you list pad numbers if any and casting dates. On a 512 it should be the top of the bellhousing on the other side to the casting no.