Any year Gen. 1 can develop rounded gear engagement dogs and mating holes. It can begin with careless gear-shifting, not being sure to properly toe-in the next gear on the way-up, and not downshifting with care. You need to match the gas to the expected load. For instance, if your downshift puts you at redline, that's not the best technique, slow-down more before downshifting.
'Speed-shifting' will probably accelerate your wear on the engagement dogs, as you're more-likely to miss a gear. That's not rolling-off the throttle, and hitting the next gear as you 'fan' the clutch momentarily, to allow the gearchange. It takes skill and practice, and every missed-shift is just resulting in dogs becoming worn as well as their receiving slots.
'Granny-shifting,' where you roll-off the throttle, and shift up, and then roll-on the throttle is less-likely to cause a missed shift, even when done rapidly. The former only momentarily relieves the gear-loading, as you 'fan' the clutch, the latter relieves the gear-loading for longer, and while not as quick, it's easier on the tranny.
An undercut gearset helps to pull-together the dogs and the adjoining gear's engagement slots, reducing the chances of rounding-off the dogs' edges.
