I know that you are looking for issues in the cylinder bores related to the excessive exhaust smoke but I believe that you indicated cylinders #1 and #2 that you recently inspected with the bore scope had no indication of being the source of the smoke (clean plugs and decent compression). While the pictured piston defects are concerning and may add to your list of concerns for the engine try not to go down every rabbit hole you find or your driive yourself crazy. If your goal is to have a resonable looking and driving truck that will get used like most of these trucks are (a few thousand miles a year at most) without the cost of rebuilding the engine step back and review what you know, what else you need to know, and how best to obtain the information.
Having a lot of air pushing out of the carburetor when doing a leak down test would tend to indicate the intake valves were open, not just leaking past the valve/seat interface.
A good running replacement engine that you can install and achieve your goal without spending money on a rebuild is like winnning the lottery, possible but odds are not good.
