Thinking the
oil pump might have something to do with this. The major load on the distributor gear is the
oil pump. If the cam gear - distributor gear were mismatched, one would think there would be even wear all around. The failure as described was a group of teeth together sheared off. If the
oil pump injested something that would make it stop turning, or a major oil flow obstruction occured in the engine to cause a severe hydraulic load, the weakest link in the chain that would break first would be the pump drive shaft, or the distrubutor gear.
Put an oil pump priming tool on the pump drive shaft, and see if it turns. See if it turns with equal resistance with a full rotation. If it doesn't turn at all, or binds in one spot, pull the pump out and find out why. When I pre-oil an engine, it's not uncommon for the drill I use to smoke and get hot. The oil pump uses a lot of torque to turn it, but it should still turn freely.
Just a thought. Don't want to do all that clean up and have it happen again.