sounds like a cool build. while i dont have any first hand experience with turbos, i did sell a magnum 318 to member of forabodiesonly.com

he has a k-car that runs 10's (check on u tube!) on the turbo 4cyl and said he wanted to build a turbo magnum 318.

anyways, i will try to dig up his contact info, but you might want to try posting there in the tech section to get a hold of him.