First, it is a press on pulley correct? It should be if it’s original to a 1983, the earlier (like late 60s) pumps use a keyed pulley with a nut on the shaft.
Remove the belt, if you have a dial indicator use that, if you don’t find a sturdy wire that can be shaped (like a metal coat hanger, Tig rod, 12 gauge copper wire, whatever), get a length and fasten to a bolt nearby, bend the wire to make a probe.
Set it up at the green arrow at the face of the pulley, grab and try to rock the pulley side to side, observe for a change in spacing from your probe, this will tell you if there is bushing or shaft wear.
Then spin pulley to find the highest spot, bend your probe to be closest to that, slowly spin and observe for changes in the gap. You can also set up the probe in the groove of the pulley where the side of the belt contacts.
Then move the probe to the yellow arrow, perform the same procedure and observe for changes in the gap.
If you have a dial indicator, do the same except you have actual numbers to work from. Hopefully this makes sense.
If you see wobble at the green arrow, but none at the yellow arrow, that would suggest the pulley is bent, if runout is observed at both that leans toward the shaft being bent. I wouldn’t expect that shaft to be bent unless it was subjected to really hard abuse. The pulley would be the easiest of the two to deform.
There are a couple assumptions being taken doing it this way, I can elaborate if needed. But it should provide a basic idea of what’s going on.
Let me know if you need clarification for any of that. It’s easy to demonstrate and explain if you were standing next to me, little harder in writing.
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