The position issue has been thoroughly worked over several times before, going way back into Shelly's Fordbarn. You need 5/32" forward movement. Too much for either gaskets or a spacer, as you will lose the engagement of the starter face alignment flange into the flywheel housing casting.
The best solution is to rotate the starter shaft and cut a new Woodruff key slot and a carefully measured location spot drill 5/32" forward. This will leave you with a shaft that will accommodate both types of drive. As an alternative to cutting a new Woodruff key, you could weld up the old spot-drill and move it forward, but then you could not go back to a Bendix.
I have found three different manufacturers, the 'throw' on all is slightly different, all much, much less than a Bendix. One jambed in the extended position when the internal helix cracked. Another had a stick, or hitch in the travel. Disassembling it revealed an extremely crude, rough machined helix that was glass-hard and brittle. Annealing it at 700F left it in a workable condition where I was able to clean it up with a Dumore die grinder. It has been OK for about 100 starts. The third had such a short measured travel it would never be good for more than 75% engagement.
I'm now thinking the old Bendix is best, just be careful not to buck it with too much advance at startup. If someone came up with a lace-on synthetic fiber scattershield for the spring and end-piece to keep thing in place if the spring or bolt fails, that would be great.
