ABS or non ABS doesn't have anything to do with wheel size. The wheel bearings are different to accommodate the front wheel sensor.
Are you planning to try and fit an OEM wheel or aftermarket? The earlier Deuce and Rocker wheels are 21" and so is the later Breakout wheel; the Deuce wheel is 2.15" wide and the Breakout is 3.5" wide.
I don't believe you will need to raise the fender; you don't need much clearance there, just enough to accommodate tire expansion from heat.
It will take some patience and mocking up and measuring several times but it can certainly be done. Select the wheel you want to use, strip down the front end, mock up and measure with the OEM spacers. I usually order a bag of shims from McMaster Carr to fit over the axle and use the shims to set the wheel so the rotor and caliper align. Then order some wheel spacers a bit longer than required and have them trimmed to the proper length.
You can order wheel spacers from Vulcan.
Axle SpacersMotorway Engineering Co.