Outworld, the trouble with the long pulley water pumps in your 45 truck is that when shortened, the fan will hit the balancer and lower rad hose. Plus the fan then will be way low on your radiator, should be higher for best air flow.
The better solution today is to buy this adaptor plate that allows you to run the 216 water pump on your later 235/261 motor. I've seen these adaptor plates on ebay about $40. As hard to find nowdays as the 235s/261s are I wouldn't pass up a good deal on either one. You could waste years hunting down the 261.
The really smart solution would be to find a 53 235 out of a pass car that had powerglide trany (first pressure oiling motor) or any 54 235/261 as these motor came with full pressure and the early style high water pump as did your 216, bolts right in no sweat. Happy hunting.
