Cause of Engine Knock in the 6-226?

My '58 pickup has the 6-226 engine. When it warms up (run it for about 3-5 miles), it gets a really bad knock. It is the worst when the engine is running mid to high rpm. When the engine is cool, it goes away, or is very slight.

New Willys owner, so what I'm looking for is a couple of things:
-What could be causing the knock?
-Is there an easy fix?

The previous owner said that it was a wrist pin. I'm not sure, so I wanted to see if anyone else could weigh in. Yes, I am using Lucas Oil Stabilizer. It helped, but didn't get rid of the knock.

Any info is appreciated!

The Hurricane 6 is a great engine...try removing the plug wires one at a time to see if the knock goes away or becomes less noticeable...do this when the engine is at normal operating temperature...this way you can isolate the knock...unfortunately there is no quick fix here...you will have to disassemble the engine to make permanent repairs...you might buy a little time here, and I mean a little, by using a heavier motor oil, such as SAE 30W or SAE 40W...don't use a multi grade oil until the bearings, both rods and mains, and wrist pins are within factory tolerances...you will never get rid of that knock...it can only worsen...I'm sorry but it looks like an overhaul is in you near future...maybe you could rebuild another short block and still gently drive the knocker until you finish it...good luck, sir.

Yeah, I am planning on rebuilding the engine. I was hoping that there was an "easy fix" that could carry it until I can get it rebuilt. Thanks for the info!