318 heads

Myself, I wouldn't fool with changing perfectly good heads unless going to aluminum to save weight. Many claim Magnum swirl port heads are much better, but others claim not and there are many out there with cracks between the valve seats, or perhaps imminent cracks. Magnum heads also require an expensive aftermarket intake manifold, unless you use their factory MPFI "beer keg" intake, which might be smart for a driver in a $5/gal future.