Hi nogo69,
I think Hoyt is right if the 53 motor is a full pressure block it may be the better fit. The 261 would be nice, but out of the choices you have. I would go with the 53 motor as long as it is a full pressure motor. I believe you can use the 848 head you have on the 53 engine, if not the original head will work fine. It is better then the original 49 motors. The thing about using the 55-62 235 is the water pump is longer toward the radiator and you will have to make adjustments or modifications, or you can purchase a water pump that adjust that problem, kind of pricy in my opinion. This is the same for the cars or trucks, that is why the 54 motor is always the one of choice for cars and trucks pre 54 less modification, and full pressure oiling with the same style water pump. The 53 motor that was bolted up to the automatics were the first full pressured 235 motors. I hope this helps some, good luck with your project and I hope you get the right motor.
Steve
