After installing 21x3.5 on the front of my Road King, I opted for a 19 on the front of my Fat Boy. Just make sure to get a wheel wide enough (at least 3") to run a 120/130/140 tire to keep handling in check. While you shouldn't have to do anything to the fender, keep an eye on the tire clearance. Some tires (like Avon) will grow a little taller when heated than others (like Metzellers).

Good luck- you'll love the look.

 

I have a 21x3 on the front of mine and have no "tracking" issues. I opted for a 90/21 Avon as I wanted whitewalls. If I was going to go with black walls I would avhe gotten the 21x3.5. I got a 16x3.5 rear which is the same size as the stocker. The main thing I noticed when the wheels were first swapped was the weight of the larger front wheel. The 21x3 handles great. I suggest a stickier tire, but it really depends on what you have now. I went from a 16x 3.5 to a 21x3 so i have a smaller contact patch. I also have DNA's and nary a problem after nearly a year. I ride a lot as well.
You'll be fine with the stock front fender and the stock rear wheel will be fine too if you want to leave that.

 

I have a 18x3.5 in the rear and 21x3.5 front. No handling issue except for the "heavier" front setup, if you lower the rear only you'll notice the front wheel heavier because of the increased stress on the rake joint, same effect takes place when the difference in between both overall ratios gets bigger, like a ride with 16 vs 21" which leaves a prolly one or two inches plus what you decide to lower or already have lowered you rear setup. Take this into account.

Mimo.

 

21 inch in the front 16 in the back. I have the MH90H21 (3.7) x 21, Wide Whitewall as a my front tire. I got no complaints it rides smooth and handles great.

 

Yeah... but you do have beach bars my friend how is that for leverage
I switched from beach bars to 18" apes, there you'll feel the difference. Even when I had my stock 16" wheels setup, just dropping only the rear created a way more "heavy" front wheel... and back then I had wide beach bars.

Mimo.

 

Hafta agree with all here...21x3 front with 120/90x21 and a 18x3.5 rear rim. This is the best mod I have done on my bike to date!

 

Yeah your right Mimo but I did lower the front end by 2 inches with the progressive kit. It fixed my heavy front end feeling. I got 18 inch carlini apes on my heritage and it's definitely a difference between both bikes. After lowering the Deluxe, I haven't had any issues

 

You should do an 18x4.25 if you are going to do the rear unless you want whitewalls. It will fit under the fender.

 

Placing a 21" wheel on the front of a Deluxe or Heritage is one of the most attractive mods that you can do. IMO, I think that it looks much better on those bikes when you put a whitewall tire on it. I went with a 21x3.5 and have found no changes in the handling. I wouldn't go any smaller than a 21x3 due to the weight of these bikes, but I know some others have an enjoy it. The Heritage and Deluxe fenders also don't require modification to fit the 21" rim.

 

I have the 21" front and 18" rear. My bike lowered a bit more than an inch. Crappy blackberry pictures.