Are the water pump pulley sizes different between both motors? If the 6.0 pulley is larger than the 7.3 the fan may be overspinning causing the failures.
Same pump I ended up using for my conversion and it definitely runs circles around the stock ford pump and no whining either. Looks like we both modified our brackets identically. My main goal was allowing for a stock pump to be used still just incase the pump failed ever and a Saginaw...
Not sure what brand they are, but I don't think anyone would pay that much for a short shifter considering midwest use to sell them for $175.
I'm sure he would make them again if there was enough interest in 5 speed ones. He still makes the 6speed ones for $175