Well, that is a new one for me, for a small block Chrysler pump.
Poor quality control – I guess.
For me (personal cars), the '60's reman cast iron water pumps and high RPM's = ball bearing problems. I went through a number of them with my 340. Not saying it was the problem but I finally removed the fan blade/clutch and went electric fan. I'd see over 6 grand often with that car.
I have gotten to the opinion, for the cost difference, to just go with new water pumps.
BudW