The baulk (synchro) ring has been the same since 1962, but surely you're not reusing the original ones. These rings slow down the gears to insure that they mesh without crashing. They have a friction surface on them that is the first thing to engage the next gear when shifting. The height the ring sits proud of the cone surface indicates the wear, but the common sense approach is to replace them. These are factory originals.
"Fit each [synchro ring] to the tapered cone on its corresponding gear. There should be a clear gap between the inside edge of the ring and the gear, around .063 inches/1.6mm where a new ring is used on a new or little-worn gear. Less than 0.031 inches/0.8mm means the ring needs replacing. If this dimension isn't greater than one with a new ring (the gear cone surface is worn) a new gear is needed." Fits the smmoth and rib case .