RE: 63 FZ top end rpm
The pin on the crankshaft is steel so it should not be showing ill effects from the connecting rod bushing wearing out, that is the reason for the brass bushing in the rod.
As for the ring, you would need to check the actual end gap on it as opposed to when it was new....too much math, just put a new one in as they are cheap insurance. The parts you need to put in this engine are still going to MUCH less expensive than a new engine. You're looking at a ring, rod, bearings, gaskets and a bit of your time thus far unless you found some other items that need replaced.