The simplest swap would be a '54 235 (car or truck). It has full pressure oil system, insert rod bearings, and the water pump locates the radiator fan in the right position.
Another simple swap would be a '53 235 from a car which originally came with a Powerglide transmission. It is very similar to the '54 235 with the exception that it came with hydraulic lifters and aluminum pistons.
Later 235s have the water pump located in the wrong place for your radiator, requiring a water pump relocating plate.
Carl
