(quoted from post at 09:53:33 09/22/17) I would suggest taking the distributor apart and find out what made it stop turning. Most likely the shaft got bent, as when the distributor stopped turning while the engine still was turning the gear on the camshaft that turns the gear on the distributor shaft forced the distributor shaft forward causing the cover to break. You will need to inspect the gear on the end of the camshaft closely, it may have been damaged as well. Also you need to make sure that no parts of the cover are anywhere inside the motor. If you cannot account for all of the parts of the cover (put it back together like a jig saw puzzle) you may need to drop the oil pan to be sure you do not have any bits inside.
Make sure your replacement distributor is put together right, has nothing loose inside, no long screws mounting the points and condenser that could contact the advance weights, etc. We bought a tractor last year with broken cover and distributor. The previous owner said they were trying to start it by pulling with a pickup. He said he "dumped the clutch and the distributor cap popped off". They had spent a lot of money and done a lot of work to the tractor, but after that they just gave up and bought a new 4WD tractor with FEL and put this one up for sale. We got it for significantly less than the asking price, but it was still a lot of work to get it in good running condition. We were lucky in that the distributor drive gear on the camshaft was not damaged and no parts of the cover got inside the motor. I was able to get a replacement cover and distributor from a local guy who deals in parts for old tractors, Fords and Fergusons mainly. Have read where the new replacement front covers sometimes have bolt holes that don't line up right. Good used parts are usually better than new.
Best of luck with your endeavor.