My 4x4 system was made specifically for an AD 2 ton, so you can't consider mine an engineering masterpiece. Sounds like you have some big plans and I'm sure the problems could be figured out. If you want something capable of doing 65 mph, I would try to find a later model frame/running gear and swap the body over to it. I think it would be safer and easier to do as well.
Good luck, George
