I put that gear and hardened hex-end shaft in my RB when I changed the cam. Got it from Hughes. Remember, they expressly state on the instructions to only use it with a new cam. I guess the operating dynamics are much like a ring and pinion set. Keep them together once run.

Also, use a distributor shaft collar to limit how much the hardened gear can climb the cam gear during operation, which can dramatically effect the contact pattern between the cam gear and driven gear.