I've heard rod knock on an SR before, bad rod knock (spun bearing). I've also heard it on a KA in a video. This isn't nearly as loud or "rattle-y" but it does get faster with rpm and does go away when you take away fuel or spark. You mostly hear it at idle and in the 2k-3k RPM range but I can't tell if it goes away at other times or is just drowned out by usual KA truck noises. I did find a post on ka-t that said mild rod knock can start at certain RPM then progress slowly to total failure.

I'll try again to isolate it. I had a screwdriver on the oil pan under cylinder 2, on the valve cover above it, and on the intake and exhaust manifolds/ cyl head at 2 and couldn't hear it through the screwdriver.