Thanks guys. The other areas of the piston actually look better, no detonation or real signs of wear or blowby, and within spec. The pic is of the only area that was a little bit of concern because of blowby pattern (wasn't sure if that was a function of rings being old or something more worrying), but it sounds like it is likely in good enough shape to continue.

Learning a lot doing this with Scott V.'s help! No shops around here have experience with NSRs so it has kind of forced my marginally mechanical hands to learn to do more. fingers crossed.
_________________
-Jim
'93 MC21