Cutting A833 Input Shaft Question

Im new to Mopars and this is all new to me. I have two now 72 Duster /69 Roadrunner . I’ve always liked them but they’re scarce in the area I live in. I’ve been building and working on Chevys for over 40 years.
How deep can I safely go on the drilling? I’m afraid if I don’t drill this somewhat. It’s going to put the pilot bearing forced against the taper on the shaft at the clutch splines. I figured if I added even a 1/2” more depth will lessen the amount of cut required.