Ok I have read this thread as it has been building on this gear problem. I have seen the standard "It has to be the
oil pump" answer and let it go to see were it would go.
I would like to point out that with the HV pump the amount of pressure put on the gear is no more than a standard pump. Any
oil the engine can not use is pushed out of the by pass.
One thing I have not see anyone ask is if you have tried to use a stock distributor to see if it breaks the pin. I would bet money it will not. If you are breaking a pin on an aftermarket unit drop in a factory unit to see if problem goes away. If it does it is the aftermarket unit.
If it does break the pin you have another problem.
Oil pump gear set may be to tight or trash in the pump gears that causes it to lock up. If it is set to tight from the factory when it gets hot it will lock up and shear the pin. I guess you could say that is the fault of the pump and it would be but not because it is a HV pump.
Also be sure the gear is getting well lubed. Pull the distributor and spin up the oil pump. You should see some oil spraying into the distrib hole near the bottom that keeps the gear lubed.