what does it mean when piston tops look like this.

what's the surface like under the crap? Does it come off? And how easy? Is it clearly on the surface, or is some of that burned piston material?

The only piston tops I've ever seen were grayed with fine soot, otherwise looked like a new piston. No idea how many miles were actually on the motor, but it was a factory 289 swapped into a '67 390 Mustang GT sometime prior to ~1987, so anyone's guess as to the origins, mileage, and "stockness" of that motor, but it looked nice inside I'm guessing that was an ideal case after seeing yours

It doesn't look catastrophic, more like oil residue forced up past rings. That could be caused by a blocked PCV valve AFAIK.

What was the engine doing before you took it apart? Was it smoking badly? What color?

That clean spot almost looks like oil, or gas, or water was collecting inside the cylinders. The tops of the pistons look pitted, as if you were getting some pretty bad detonation.

You can almost see the outline of the valves. Could that be from fuel spraying through the open intake valve?

What does the clean spot line up with in the heads?

definitly a BAD head gasket