I can't say why you had a failure but often the oil receptacle on the side of the distributor is ignored--it keeps the shaft lubed. The gear is often difficult to remove. It builds up deposits of dry dirty oil on the shaft and then can't pass through . I use a solvent like carb cleaner and work the gear up and down--it will rotate as it comes up. Obviously there was a lack of lubrication. You'll need to remove all the related parts to get the whole story. You should remove the oil pump if you haven't already done so. Then you can lubricate the shaft from the bottom. I have 2 boxes of useable distributors and bases. If you're interested you can buy a pair from me for $20 plus postage. Personnally, I'd look to go to an electronic system. I've seen posts refering to various aftermarket systems. I've used the Bosch distributor, coil and control unit from the 1975 240 series (B20F). It's a direct bolt in and the control unit is simple to wire. Be sure to use the (or a) resister.