I went to the legends 21Ko front end kit and the change was night and day,I'm very happy
with it.

 

A 21" X 3.5" would be the correct size, just make sure it is for a 2012 Touring so the bearings are the right size and hub width correct. It must have tapped holes in both sides for the rotors too. As long as you put on a 3.5" width wheel and the correct tire, it will handle just fine, but the front end will sit up about an inch to an inch and a half higher which itself could make some difference. I believe Progressive has some drop in spring kits that have adjustable spacers to drop the front end as much as you want but the forks have to come out to do the install. I would recommend an inch unless you have a H-D oil cooler on the front then I would probably not mess with lowering it because the fender may strike the cooler once the fender is adjusted. You will need to enlarge the rear fender holes, I believe it was a 3/8" bit I used. Allows the rear of the fender to raise up and give clearance. Tape a 5/16" nut to the center of the tire inflated to 42 lbs and spin. If it doesn't hit, you're good.

21's are awesome but it does require some other things to be done, like described above, to do it correct.