The block casting in my 1978 Corvette is the same casting number that was in my new 1976 K20, that was a 4 bolt block. I built a 383 from a 1977 block with the same casting number that came out of a C10 and it's a 4 bolt, I'm betting the Vette has a 4 bolt block but I've never dropped the pan for any reason. I built the 383 to transplant into the Vette but now have decided to leave it stock. Any 350 should do you just fine as long as it's built correctly and to stroke it to a 383 adds great low RPM torque. The iron could contain some different percentages of tin and nickel but other than that and 2 or 4 bolt mains all of the parts are cheap, plentiful, and interchangeable.
Last edited by 78buckshot; 01/31/2022 3:28 PM. Reason: spelling
