Josh,
Did this engine come in your '54 3600? it does not seem to be the original for a 1954 truck. The information that waldo53 provided seems to be correct. There are some other things to look at:
Does the engine have the "tall" pushrod cover plate that covers both the block and the head? That is used on all 216s and the early (pre 1950) 235 truck engines. I have never tried to put a 216 head on a 50-52 235. They both have the 15-bolt pattern, but I am not sure what to do about the side plate. Interesting question.
Does the block have the oil distribution plate, on the lower driver's side? That is a sure sign of a low pressure 235 or 216.
Hoyt
