1971 340 L2316 pistons stock, modified or damaged?

Yup.......they’re on the rods 180* out(or the rod is installed backwards. Squirt hole goes towards the cam.)

Shoulda made quite a racket.
It usually raises hell with hyd lifters too.

Those pistons are about 1/2” thick in that area.
They’re probably fine, but I’d check to make sure the skirts aren’t folded in.

If they’re still being used with bushed rods, it’s easy to flip them around on the rod so they’re installed correctly.
If you end up doing that, use new snap rings.

Very likely a bunch of bent valves...... but, even if for some reason they’re not bent...... take them out of the heads and throw them in the trash.
It’s a catastrophic failure waiting to happen.