Yes, new rings can be installed on old pistons, once properly cleaned and inspected.
That is what I did on mine. I had 120 p.s.i. on four cylinders and 90, 100 on the others.
I cleaned, inspected and measure piston grooves per the manual.
I installed the old top ring in the cylinder and got...
I might have a line on some +0.020" pistons.
I just did a minimum rebuild on mine.
New rings, bearings and seals.
Intake/exhaust flatness and gasket seals were my biggest challenge.
I'm replacing all the seals and gaskets in the 3 speed and transfer case now.
I have all the PTO parts except for...