The Fatboy front is different than the glide, the glide is wider and the trail is different than the fat. The fat would be considered a mid glide. You can get the glide style nacelle for the fat.
The fat is single brake so.

 

It is a fatster.

 

Thanks for the clarification, I wasn't sure of all the specs and whatnot.

Does the single brake mean that I could use my stock iron brake setup?

The overall look I'm going for is a fatboy/heritage style forks, RK nacelle, and a fat front tire like the 48.

 

You have to watch your years but brakes are the same so are the rotors.
This is a pretty common swap, and yea a nice look.
I believe the trail is the same, axle size has changed over the years so be careful of that if you are not running the fat wheels.
Hd sells the rk style Nacelle, or you can get one on e-bay, I am running one on my fat.
Bahh humbug to anyone saying don't do it.

 

Are you sure on this?

I thought the Fatboy (pre 1959) nacelle fits right away on RK (post 1959 nacelle) forks...

If the Fatboy is a mid glide, I suppose its nacelle is a straight bolt-on on my 2012 XL Custom, right?

 

Yeah I was just wondering because in the one post they talk about having to the lower tree and to watch out for fork stop and the fork lock tab.

I was just wondering if there were years of the FB front ends that would be more of a direct bolt on with the newer sportsters?

 

Well I do not consider myself an expert on the subject. First year of the fatboy was 1990. The RK uses the same front end as the FLH, ultra. It has the forks that are very vertical and use the trees with the center mount in front of the tubes to get the trail that it needs.
If you take a RK or ultra fender and cut off the spacers/mounts that are about 3/4 of an inch you get a Heritage fender, or can use it on a fat.
So the RK is about inch and a half wider than the fat front end.
The fat uses 41 mm forks, don't quote me but I believe the FLH does also.
The XL uses 39 mm, but I believe the earlier were smaller, not sure, 35-7?
The xl is a narrow glide I am not sure about your xl custom, but the rk style nacelle needs the bolt holes on the side, and the 41 mm tubes.

 

That I cant answer, you did not mention what year your bike was, if it was me I would try to use the new brembo brake and rotor for better braking, and the newer style wheel with the drilled holes is cool also.
One note the very cool picture that Wachuko posted was not a fatboy front end, it has inverted forks so either off a import or aftermarket.

 

My bike is a 2010 Iron. I'm not really into the one Wachuko posted. I heavier look the FB front end has, but what I really like on the FB front end is the taper to the forks. Also want to be able to get a fat front tire.
I might even like it if they made some type of nacelle and fork covers that make my narrow glide look more like the FB front end.

 

So yours is a rubbermount, the fb front end used in the XL club was a 97, it has the lock under the bottom of the tree, so that is why it had to be trimmed. Not sure what you will get into with a newer front end, I would think it would be less of a hassle since both have the internal locks. Not sure of the stops also, this is something you need to just work out. I was surprised how little there is on the internet because I have heard of his conversion many times. The real early XLs had a nacelle that looked very much like the fat but was much narrower, not sure if I liked it. Love the look of the fatster though, I I still had my sporty that is the way I would go.