Did you try a piece of pipe ? You are talking about the Sprocket Hub retaining ring ? Tap it on and into place with a piece of 1-1/2" SCH40 pipe....(1.610"ID) I did this a few weeks ago....but couldn't find the piece of pipe I used.....it was a piece of cake to install with the pipe.....a real BITCH without!
Going to try the pipe trick, been using the screw drivers but no luck