help with diagnosing a knock in my engine

[rollin thunder]

I have a 1984 Chevrolet 1/2 ton c 10 with a 250cu straight six.This is an amazing find i got it for only a $100 and for the shape its crazy i have only read about these finds but the only thing i noticed wrong with it is it has a knock in the engine. It sounds like it is coming from deep like almost the bottom of the block. I thought it might be a wrist pin and i tried pulling spark plugs caps on each cylinder at a time and that had no effect on the knock. Any suggestions? or maybe it is a wrist pin and isn't the piston still moving so maybe the knock would continue? makes sense i guess i am still learning so any advice would be great