If you can measure the piston, you will get an idea on the bore size. If it has been run hard as you say, I would get the next size up piston, and take it to a reputable engine shop to get the cylinder bored. Might as well take the head there too, and get them to give it a clean up and valve job. They should also be able to reface the head if it has warped. MCMA111 likes Engine Dynamics, I think they are in the SF area. I am on the other side of the world, so not really familiar with localities. I like to use Pro-X cast pistons, but each to their own. I build my engines for longevity, haven't had one burn oil yet, so not doing too bad. I use OEM valves if needed, most of my engines are around 30 years old, so new valves should last another 30 or so years. Give the tensioner shaft a light rubbing with 1200 emery paper to remove any marks from the tensioner, small marks can cause the dreaded timing chain tic. The top tensioner shaft has small marks on it from the tensioner, these were enough to cause the timing chain tic. Bottom shaft is new.