They also have a truck version that has a 5/16" hex and a special 5/16" at on end and 1/4" at the other end drive shaft. I had it pointed out to me that it's the internal hex at the pump that suffers and the 5/16 helps with that. High volum is one thing and high pressure is the other, The two combined creaet a load, that is carried by the distributor shaft and gear and the pin that connects that gear to the shaft. It usually has a 1/8" pin ,a built in weak spot ( that is a good thing) Any larger pin will weaken the shaft and that is the distributor a lttle more, and moves the weak point (like a fuze) somewhere else, likely more expensive to repair. I found that out once when I razed the throttle before the
oil was warmed up and that pin sheared. The engine just died. It took about an hour to repair. I did find that I only had a spring pin and I did buy a true roll pin to replace it. 1/8" x 3/4" an improvement but you couldn't find any other point that would be as cheap or quick to repair as a safety.
Whe i installed the new pump I just took out that soft plug installed the single shimm they sent as an option with the pump, but I also had doubts about that soft plug and converted it to a screw in pipe plug . I played around using seceral different taps with the ends ground off to get the same depth as the original soft plug. It looked right and ended up working as planned .