I just matched up a roll pin (not a solid one) in my RC junk with a drill bit I had. I used a small cut off wheel just about worn down to a dime size to notch the diff ring on the inside. Placed it all back on the trans shaft to center it and mark where the the notch is on the slipper plate. Slowly drill a small hole for the roll pin. Cut off the extra pin and that is pretty much it.

Just take your time. It is easy to do it once slow then fast twice.