Barrels off , pistons off , rings off and ACCURATELY measure the bore and piston diameters . Put bare pistons in the correct barrels and measure the gap down the side . Pop bare rings into the relevant bore and measure the ring gap . Check barrels and pistons for scoring and lips on the top before taking any measurements - check measurements against spec sheets in Bentley. OR Just buy a new set Sent from my SM-G960F using Tapatalk
It's not easy to judge just by pics but those don't look bad and unless you go for the capacity increase, if the sizes are good, you might get away with honing the cylinders and renewing the rings. I'd fit 96mm B&Ps.
Badly worn there will be an end to the wear where the top ring is at the top of the stroke. Clean any carbon and look, feel with you finger nail. IMO if you find a ridge I wouldn't bother measuring, I'd replace. If you don't find that then measure? I'd be hoping for the ridge to help justify buying bigger ones.
