I think you would be fine with a modern or vintage Schwinn frame. There is a company that makes a Schwinn style frame with a fuel tank molded into it (ala Schwinn Phantom). I was trying to find it but couldn't.

Personally, I would be more concerned about what fork and brakes to use then the frame. Steer clear of the cheap reproduction springer forks. Especially the repro Monark fork. It looks cool but is not safe.