Mopar 318 heads

Magnums take a different bolt pattern, some intakes have both, don't think yours would.

You can do a 318 might want to lower your expectation, are you rebuilding ? a set of piston, for better cr opens up head choices to and 340/360/magnum aftermarket.
but if your rebuilding you still might want to think about getting a 360 LA to start with, not trying to talk you out of the 318, if your doing more then cam 4bbl headers, it's usually better off starting with 360/5.9l, it's gonna be making an extra 20-40 hp through out 1000-5000 powerband where most street engines need it.