The rust in the wheel tubs had caused some tire rubbing issues due to the rusted metal expanding. It was a mess, with half assed repairs (involving caulk) and general neglect. We decided to mini-tub the car...which was a first for us, plus the convertible top framework mounts directly to the wheel tub. We had real good luck keeping all of that stationary and fabbed up our own wheel tubs to go back in.
We knew the extra torque from a roller 455 was going to a lot to contend with, so we decided to put a full frame (2X3 tubing) instead of aftermarket frame connectors. This meant going through the rear floorboard, but chassis stiffness trumps back seat passenger comfort in our book.