Can I use a FC thermostat water pump housing on my FB? Reason I ask, is that when I was installing a rebuilt FB engine, I heard this small "ting". The water pump housing cracked where the bolt for the thermostat cover went cracked. Being cast iron makes it impossible to weld. The only solution was to find another FB housing which took about 2 weeks.

 

You can use an S4 waterpump housing. You'll need to also use a S4 water pump pulley, and the upper and lower S4 air pump bracket. I did have to hog out the four holes for the clutch fan spacer so it would fit the spacing of the S4 pulley.

 

Here's one I put on my 1979 SA.