Folks, if you are gonna have the heads off and there's even a hint of a ring problem, it's not too much more effort to drop the pan and install rings. Comet, ARX, Kreen, etc, is not going to put metal back on worn rings or bores. It's a lot of effort and money to pull the heads and work them over. You'll be able to tell a lot by the bores. If you find scoring or pitting, you're gonna be forced to pull the engine and go thru it. It's not clear from the first post whether the heads are being pulled to deal with issues on them or if it's to free up "stuck" rings (and how can you tell stuck rings from worn out rings or cracked rings without pulling the pistons). If it's just the stick rings do the ARX or Kreen first and see what that does. Otherwise, like RLDSL said, you are more than halfway to the rings with the heads off. In my experience, you usually regret most what you DON'T do. Pull the heads and spend that money, only to find that you are right back where you were after you've reinstalled the heads. You won't know until you fire it back up. If you are pulling the heads to freshen them up, often tight heads will make a ring problem even more apparent. You will be able to tell a lot with the heads off. If the bores look really good and mike out good, now is a great time to drop the pan, pull the pistons, hone the cylinder, install new rings and start out with a tight, sealed cylinder. With fresh rod bearings, fresh rings and redone heads, as well as replacing anything else that looks hinky, you've done an inframe overhaul that would put you in good operational shape for a good long while.
I say all this not really knowing the root cause for the heads being pulled.
