As said, Ma Mopar used the same heads with the 2bbl & 4bbl cars. However, It's really hard to make compression in a 383 with open chamber heads. If you're willing to spend the money on rebuilding a set of heads, I'd go find myself a set of 516's (closed chamber), then spend the extra money to cut in a set 1.74 exhaust valves. You'd then have a decent set of heads that would probably get you to somewhere around 9.25:1 compression with your existing bottom end. Use .020 shim style head gaskets when you re-assemble. You're going to need compression to be able to realize the potential of the larger cam.