I also think September of 1974.
I was going to say it would have been in a 1975 model year but then saw you said it was a replacement block so who knows.
I would think its a mostly complete short block, the HEI distributor is from a Corvette. So I'm thinking the compression ratio is around 9:1 so I can use regular (87) octane.
I would think its a mostly complete short block, the HEI distributor is from a Corvette. So I'm thinking the compression ratio is around 9:1 so I can use regular (87) octane.
Just checked, its 8.25 to 1 for the LS4 in 1974 and was still spec'd to use 91 octane minimum.