You can actually just grind the inside tooth edge of several ring gear teeth to get the clearance for a regular pin. The pinion gear never makes contact with the ring gear on the edge. I did it in my old 340-4spd Duster with 4.10's in the 8.25 rearend and no ill effects or noise.

I'm not sure MP still makes the special pin for 4.10 and up gears but it used to be in their catalog. A regular pin can also be machined for the notch.