That piston is junk. I would rather give a better evaluation after seeing the bore and more views of the piston but...
You have some pretty good scoring. The top of the piston looks like there was carbon buildup it was slamming into. Carbon buildup can make the engine run poorly and from the looks of the piston, oil was getting past the rings.
How much carbon was in the combustion chamber? I'm wondering what the valves look like in this engine. Perhaps this engine could live again. You will know once you measure the bore with your new tools.
Head warpage on these engines is repairable as long as they haven't been machined too many times. It can normally be repaired with a flat surface, sand paper, and some time if you don't have access to a mill.