[Mr70]

Find out the casting dates & make sure they're 4 bolt main and not 2 bolt main blocks.
Besides crankshafts,do they have rods & pistons?
Both effect whatever his asking price greatly.

Used from 1969-1971,COPO 427 Camaros/Chevelles,454 LS-6/LS-5 Corvettes,454 LS-5/427 Impala & 454 LS-5 Chevelle & Monte Carlo's all used this #512 block in different formats.If you're looking to find the LS-6 Chevelles they came in,I'd copy down the VIN's to confirm,before buying.