Its very common for that gear to break because of old age, they tend to get very brittle, if you have had this problem with a new gear I would be suspecting the cam gear is bad and breaking the distributor gear. This is assuming the gear is fitting and being installed correctly.
I just bought the car and he told me he thought the oil pump was locked up. that wouldnt do it right?
the oil pump couldnt have anything to do with it?
one more question and ill give you a great rating. what would you do pull the motor or just take the oil pan off?