The hardest work a distributor drive does is power the oil pump and a high pressure or high volume pump can cause a well used gear to fail.
Inspect your old gear to see if the teeth are generally thinned---they won't usually be stripped all the way around.If they are thinned you will find the cam gear worn also and a new gear will likely not last very long.
On these engines the distributor not being all way down is NOT a very likely situation because the hold down clamp pulls it into mesh with the pump drive shaft.
Exactly the same as small block v-8

Bob Taylor