I know that I need a adapter plate for that, Summit sells one but is it hard to make adapter plate myself? How thick that plate should be? Anyone got measurements?
I would not be surprised if for $50 you couldn't find a usable Chevy transmission instead. You could certainly find a core that would give you a good Chevy case to swap the internals into. Years ago my brother actually took a BOP TH400 and drilled a couple of new holes to use it on a Chevy. Far as I remember it worked out real well for him.