Ted, Edelbrock makes a Performer RPM Airgap for Magnum motors. Summit sells a Chinese knockoff called a Crosswind. A long time ago, a Moparts member had a jig to redrill Magnum heads to fit an LA intake. If I remember right, it disappeared and has never been seen again. Check on Rock Auto for a 5.9 flex plate. The harmonic balancer and the flex plate have to match on Magnum motors. As for Magnum exhaust manifolds, there are different versions. The most common have 1 7/8 exits, and the better ones have larger openings. 2 1/4, I think?