I have a 1955 Bel Air frame for sale. It is a little on the rough side, the front horns are a little bent and it is missing the radiator bracket. However, it is straight (measured across the body mounts and the back)
Additionally, I have a 1984 Corvette C4 rolling chassis that I was going to use to convert the rough frame to a hot rod frame. This involves cutting the cross member off and welding in stuff from the corvette. The vette has a complete front and rear suspension, as well as a complete brake system. The car was a manual trans, so the differential should be able to handle the power that you put in it. It is also an independant rear end with posi-traction. Should make one hell of a car for the right person!