Why are you rebuilding it? If it ran fine before, it's considered refreshing IMO. Look at cylinder walls and see if you can still cross hatching all the way to top with no smooth spots or areas where its darker than the others, which indicates blow by. If there is nothing wrong with the compression and the cylinder walls look great, do not remove the pistons, just leave them in there and replace the bearings and headgasket. On the SR if you don't have the correct hone, or have a hot rod shop do it, the walls will be too rough and the rings will never seat right. Take off head and then post some pics up, also if you are having oil pressure issues, and your bearings don't look brand new and have wear marks on them, crack open the oil pump and see if the clearances are tight.