Turns out it was the alternator bearing that went out not the water pump. With the mechanical fan it's nearly impossible to hear anything inside the engine compartment. Took the fan off, spun the water pump and it sounded good, tried the alternator and heard a "squeal". Replaced the alternator with my spare and it appears to be all good again.
While putting it all back together I thought I'd experiment without running the mechanical fan. Truck idles around 650rpm so how much air could the 15inch mech be pushing? Last night I went to a local cruise/rod run with roughly 150 other cars for a 1-1.5hr drive, some highway but mostly back roads and subdivision driving. Weather was around 21C.
Turns out the 10 inch electrical fan set up as a pusher struggles on it's own without the mechanical fan running in tandem. Truck mostly ran 190-200, hitting 210 on a slow uphill crawl.
The truck is so much quieter without the mechanical fan that I'm going to try running a 14inch electrical puller fan and see what happens. I'll be keeping the 10inch installed and throw the mechanical in the truck box for just incase moments. I know the small electric and the mechanical work well in tandem so if it's necessary I can always go back.
