No modifacations at all, just put her on.
I'm sure you have this worked out already,, BUT,, just in case you havent thought on this. Dyna changed axle sizes (please anybody in the know for sure , jump in).
I believe 3/4" before 06' in 06' it went to 1" and in 08" they changed again to 25mm. So depending on what combination you have, you might have axle and spacer changes as well.
But what ever you run up against its well worth it..
And again no fender problems at all for me..

 

I had to drill out the holes on my fender mounts for extra clearance, my tire started to rub after hitting speeds around 100mph. Sounds like different tires expand more then others at speed.

 

That's gonna look real good. I've got wide glide front end on my bob and I just recently went with a 21 x I think 2 and a half. Its not as wide as I wanted but I went with as wide of a tire as I could without looking goofy and I think it looks really nice. I almost say they should have came like this

 

Every bike in the Dyna line-up (besides fat bob) deserves a 21" front IMO. The 19" front is weak sauce.