You migth contact the Planes of Fame Museum. They have a Convair 240, restored it to ferry shape, and flew it from Chino to Arizona where it is now. If you are a legitimate entity, they might share manuals with you.
You'd have to pay for the copies yourself, but they might allow it. Ask for Steve Hinton and don't ask for it free of charge. Everybody tries that one with a predictable answer.