Tony,
I will offer my unsolicited opinion. I read your first post on this subject. The oil pump is the absolute last component to wear out...it runs in oil its entire life.
You said a lifter started to 'clack'. I guess the rig you were driving has hydraulic lifters?
If the engine doesn't smoke, and runs relatively well, it certainly isn't in the 'dumper'.
If you are really concerned, you need to stick a test oil pressure gauge on it and confirm what the readings are.
These rigs can run with barely any pressure, and lifters sometimes do make noise.
I think you might be worried about something that isn't critical right now. If it runs alright, you might consider a heavier weight motor oil.
Does this engine have hydraulic lifters? They would be suspect before the oil pump. Dump a quart of ATF in with the next oil change and give them a little cleaning.
Stop for a moment and figure out what it is you are trying to accomplish. Its an old truck...all of it!
Stuart
