Pics of pistons especially no. 1# please.
An easy way to measure bore taper is with an old ring. If you place it in the bore & measure the ring gap at various locations, say every 1/2" from top to bottom, (you can use the piston to push it down square). Calculate the difference between the largest & smallest gaps, divide the answer by 3.14, this gives you the measure of the taper (bore diameter variation) without needing a bore micrometer.

I use paint stripper to clean pistons (not the caustic based type), that way you dont damage the ring lands. Maybe biodiesel would work.

Dont get too worried about a few scuff marks on a piston, slop in the bore is more important.
Are the compression rings stuck ?

Happy hunting

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