Just replacing a brass ring will NOT necessarily fix your problem. You need to have a hard look at the gear itself, particularly the machined cone surface which interacts with the synchro ring. Lay a new ring on the gear, if there isn't much of a gap between the small dog teeth of the gear and ring(when viewed from the side), then the gear is likely the culprit. Not nearly as common as ring wear, but you do need to watch for this, especially if the unit had new rings when it was overhauled.

If all that checks out, and the dog teeth on the gear arent beat down from missed shifts, then take some 600 grit paper and sand the machined cone surface of the gear before you put it all back together. Also, if you are getting some "jump out of gear" issues, expecially on decel, then you had better take a hard look at the hub and sleeve for 1/2. Normally when these components wear out, the end result is the condition you are experiencing, especially if you had the linkage adjusted properly and the dog teeth on the speed gear are good.

MB