It is so EASY to drop a 455 engine/trans into a 55-59 and one doesn't have to worry about any head, crank, intake, or other fitment problems. Got all the motor and trans mounts along with the frame perches from Chassis Engineering and I'd bet it was less expensive than boring,stroking, machining, etc. IIRC CE offers the mounts in either bolt in or weld in application. If the goal is to bolt a bigger cube engine onto the factory mounts then disregard the above.
