Don't you have to final hone those cylinder walls yet after boring to fit each piston to each bore ? That in itself may be enough to reduce your area of concern at the top ridge area.
I would take a .040 piston ring and slide it up and down in the bore by hand near the top of the stroke. Doubt it will be anywhere near catching on the low spot that did not clean up.
Those piston rings are round and they will ride over whatever low spot is left behind.
You may have to go back to the .040 piston plan yet if you can't find the .060 pistons.
A little extra hone on those 2 cylinders at the top to help clean them up, the new rings will expand out and and take care of the situation.
Steal from Peter to Pay Off Paul . . .
Then you are not cutting another .020 out of your bores to get to .060 and run the risk of getting into the water jacket.
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