Hey guys,
Late last summer the shaft snapped on my power steering pump. I then put a used unit on it from the pick & pull, and it worked until now, but was weak at slow speeds, and didn't work hardly at all when the wheels were turning in deep gravel or mud. So I finally went and ordered a re-manufactured pump from Rock Auto. Went through the Mopar shop manual procedure for bleeding the new pump. Went for a test drive and didn't make it 3' before there was a clunk and no power steering at all. Yup, pump shaft snapped on the new unit. Is there some other steering problem in the system that would make this shaft break, or did I just draw a bad re-man unit?

Assuming the basic Saginaw pump, they are known to snap the shafts. There's an undercut in the shaft and they snap there from time to time.
Use the warranty...

WOW, I never knew there was such a issue with them breaking. I did a search online and apparently it is more common then I thought. Not just with the mopars but with chevys too.

Same basic pump. Pullies and reservoirs change with application. In the last 70s they made changes to metric threads ad o ring fittings but with the right combo of parts you could put the 01 pump on a 71 car.

While the Saginaw pump can fail its usually for a reason. With that many failures you should consider an inline filter in the return line. Most pump companies suggest doing so just for that reason. They inspect the damaged returned warranty pump and find foreign material causing the failure.

It's got a NAPA reman unit on it now, and has been working well for a few days. So I suppose the RockAuto unit had a fracture in the shaft or something. The NAPA unit also included new O rings and a nut and bolt to pull the pulley onto the shaft, rather than using a pulley tool. I like the nut and bolt better.

What type filter am I looking for, something like a riding tractor spin on oil filter to plumb into the return line?

Looks like an inline fuel filter. I had one on my Dakota, it was brand new and leaked like a sieve! I removed it and haven't had a problem since. Just get a good one if you're getting one.