so...this is what i found (something similar, but not to the same extreme)

There was a loud knock on the valve cover only upon firing up the motor...only did it 2-3 times then stopped.
previous owner said its the forge pistons getting "piston slap" because the piston needs to warm up and expand into the cylinder.

...said he had heard it before and never did anything about it and the engine ran great (and strong!) with no issues.

to me it sounded like somethin goin on with the rocker...whatever....i used it as a vantage point to take a few hundred off the asking price.
there was no damage....pushrod was still straight....just reset the stud with some loctite and im on my way.