not hard to just remove the rocker shaft and lay them out in order and check them. if it is as simple as cleaning out the hole in the shaft or even get the plug out of the end of the shaft and flush it out good. and put it all back. actually if you don't swap any parts to different positions the clearances will stay the same and if you find a bad bushing you can change it then. I have even heard of rolling the shaft over so the top surface which isn't worn is on bottom but depending on how the holes are located this might not work.if you do that you definitely need to re-do the clearances as the height of the rockers would be less.