Preferably 2017 fatboy low 

Hi SSS. I assume you're talking about a swingarm assembly?

I think I have seen threads on here before. More than just swapping it over. Alignment of belt could be a problem. Having said that, breakouts have wide bums. Good luck with build. Post pics.

Have a look at this youtube

No just the struts as they have a different offset. I have a wheel on the bike in the original swing arm. I just didn’t want to space out my original struts to suit the wider fender as it’ll look a little odd. Rather a strut with a greater curve/offset. 

The fatboy has a similar tail light setup so at initial glance it’ll still have the protruding tail lights similar to the slim, instead of streamline lights. 

Check my pics 

 Cheers.