Either blocks will be ok, 54 is great because it has it's water pump in same location as your original 216. If you go with later block it most likely has the low water pump that will need to be modified to clear as it's water pump is longer and lower on the motor and fan wont clear. My buddy has eliminated the fan and gone with an electric fan so solve the problem and there is an adapter plate that can be installed to let you go with the original pump/fan. Been clearing my shop of 47 coupe parts lately if you need anything send me a note, most stuff is already gone. Best of luck Jim
