Since you have a 56 235 a shortened warter pump might be needed,there are two different versions out there. One is sold by Jim Carter that has the 216 sized pulley and the other sold by Patricks has the later 235 sixes pulley,on the 55 to 62 sixes the water pump is longer and sits lower in the block then the 54 on back motors and sometimes a stock fan can not be useed with the shortened pump as it will hit the balancer. There is a third option that is a water pump adapter that allows a 54 on back water pump to be mounted on a 55 to 62 motor which I have on the 57 235 in my 37,I hope I am not confusing you with all this info but sometimes a motor swap is not as easy as it seems. I dont think there is any issue with water pumps on the GMC motors and the 54 235 seems to be the best motor to use as its very similar to the 216,I know nothing about a 207 motor as I never owned one or even looked at one very closely but I wish I would of used the 54 235 in my 37 and would of been nice to have a computer when I was putting it togather for the first time. Jeff
