Oil Pump shaft broke

I broke an intermediate shaft with a Ford 390 one time after putting a high volume oil pump in it and using the stock intermediate.
When I started building Mopar stuff as a teenager I did my homework and I talked to people so I have never suffered this personally with my Mopars ..because I have always run the hardened intermediate shaft w/the pinned gear... because all the old timers, and all the books I read before I started.. said ...you will either A. Twist the tip off... or B. spin the gear.
It's good to prepare