I didn't think you could put magnum heads on 91 and ealier 318's because bolts don't line up? Pardon my stupity but whats an airgap. I'd definitely be interested in the 302 heads.
Sure can! The heads bolt right onto the block. There are only two lengths of head bolts used on magnums so you need to use magnum specific head bolts. An LA intake will not bolt to the heads unless you redrill the heads or the intake. However, Edlebrock (RPM Air-Gap) has a manifold specific for the magnum head, MP has two and Professional Products has one that is drilled for both style heads.
You need to use AMC style lifters that oil through the push rods and hollow push rods to get oil to the rockers. The only other differnence is the magnum head uses 10 bolts to hold on the valve covers and LA's 5. However, the 5 on the LA line up with 5 of the 10 on the magnums. I am using LA valve covers on my magnum heads and the seal just fine.
The picture blow is of my 360 (78 block) with magnum heads, notice the intake mounting. Also, I am using the Professional Products CrossWind intake which is pretty much a copy of the Edlebrock Air-Gap.