Waterpump

[pearce trucking]

Quickserve has it in parts and service manual section. It has a housing and "guts" seperately.
Assuming it's an 871, you'll just remove the alternator and a/c compressor (shouldn't have to open up the system) to get to the bracket that holds them. I can't remember if the fan hub is on top of the bracket or not. Then the pump is easy to access.
Oh, and I just saw your a/c thread. Have you replaced your crankshaft damper and or belt tensioners? That could cause wear on your accessory components. Just a thought.