73 340 oil pump

Every time I heard that squeal from inside the pan, it was a seizing rod bearing. But don't worry,it goes away after a a minute or two.Then followed be the dreaded rod knock.

Each time it began, was after a spirited romp, with a low oil level. My last engine now wears a 7 quart pan, and I did the oiling mods; and now she is happy to go 7000 whenever.
So, yeah, I agree; it's at least crank inspection time. If still at the squealing stage, you may be able to get away with just a lil polish,and replacing the probably spun bearing, on probably #1 crank throw; or possibly #3. I only got a minute or so warning at idle, then the crank locked up and she stalled.