Your easiest/quickest and probably most reliable way to do this would be to get a transmission with a 1" GMR chain. These are very tough to find as they are not made any longer. Once the trans is built and solid, I'd think a turbo with cam and a few other goodies are the way to go. Researched and done properly 450whp should be relatively doable. Having gone the one of everything SC'd route, it's much costlier and you'll need a ton more stuff to get an SC build to 450whp.