Bad alternators usually whine or squeal... Remove the belt and run the engine up briefly to see if the knock remains or is gone when the alternator's not spinning.

Noisy oil pump? First I've ever heard of that.

I'd still be suspicious of the timing gear. They can fail several ways, not all obvious to the eye. And they make a significant knock before they croak.

Before a new motor, try your new timing gears.... A lot easier....

And listen at the t-gear cover with a mechanic's stethoscope.
--
Don Foster (near Cape Cod, MA)