swapping to keyed
goI' ve done two, helped on three others.
Go to the double bearings, its a must do.
buy the splined shafts from POL., shop for the sprockets, I have several 17 tooth that you could buy.
If you just look at the complete parts list, looks like you have to buy a whole new brake setup. We found it was simpler cheaper and lasts, to just cut one of the female splines on the new shaft where the disc goes deeper to 1/4" and run all the old brake setup. this is not a part that ruins and screws the shaft if you run the 1/4' key.
Beware that from kit to kit and looking over the spacers necessary, you might not have the right ones, and even with the right ones your chains may not perfectly align. Go to a good steel supplier, and buy the closest heavy wall steel tube and cut spacers to fit, sitting at my desk I don't recall the size, just take an old spacer to them and buy a stick of pipe, it will have a slightly bigger ID ...works as good as, for $15. Its worth the effort, besides you need new bearing to start the season anyway.
Bearings, ...............the polaris bearing are good quality and priced right, don't figure, but go with quality and compare .
If you need to put in the double bearing, it helps to have the jig out of the old TS conversion kit, makes drilling the hole correctly a snap. If you can't find one pm me, I have had several and mailed them out for use, and I think at lease on came back last spring.