[David R Leifheit]

Take no chances.
I was using my truck, rev'd it up and it started making a tap tap tap noise. I figured it was something minor.
When the rod cap came off at 55 and locked up the engine (the force caused the piston rod to spread out, instead of a "U" shape to cup the crank it was almost a "T" shape. Couldn't get the piston out the top or the bottom) and when I took the heads off I found the imprint of the valves in the top of the piston. It tap-tap-tapped for months before it came apart, what was happening is that I must have spun the bearing out or something, but the rod cap started coming loose and the tapping was the piston smacking into the head.
I was not very knowledgeable about engines back then. Learned a lot since.

You mentioned, I think, taking the pan off and looking... well, take it off again and see if any of the rod caps are loose... check the nuts to be sure they aren't "loose" even a little.

Although, if nothing on the bottom looks bad, and the valves don't look bad either... then you are left with the pin... possibly.

These old trucks will take a lot of abuse before giving up. One I bought ran rough, but ran well enough to load onto my carhauler. Drove it right up the ramps. When I took the heads off, it was literally running on 2 cylinders. On one side there was no head gasket between two of the cylinders and the oil gallery. On the other side the head gasket had a "tunnel" between two of the cylinders and was just starting to make a bigger connection.
To be honest, I was surprised it even ran, let alone had power to climb the ramps up onto my hauler truck.

These are hearty trucks with strong engines. But if the engine is talking to you "tap tap tap" then listen and find out what it is trying to tell you before it gives up and just fails.