So; both front tires are essentially the same dimensions, Klock Werks makes the mounting adaptor, would I be the first to put a Switchback front fender on a Fat Bob? I'm after the early sixties FLH look; I really liked the origional FLHS...but now with twin cam power without current FLH weight

 

Yes you can. AFMM3, bluangel73 and myself did the Fat Bob trees on our Street Bobs, using adapters for the stock street bob lowers with adapters like you said. Their was a guy that did his fat Bob a while back with the adapters you mention. Adapters sold from Klock werks are street bob and Fat bob specific as the bolt pattern differ on the sliders for each bike. AfMM3 went to Softail FL front end as well as I not so long ago. Heres a section with lot of info that may help you. https://www.hdforums.com/forum/group...est-group.html

 

Technically, I used a Deluxe fender, but I am pretty sure they are the same.


I did have to mod the Klock Werks brackets (Wide Glide version) because they were to wide for the setup I was using, might not be an issue for the OP. I say this because the OP will be using (I guess) his original Fat Bob trees and Fat Bob lowers and able to use KW bracket (KW05-02-0107-R {raw} or KW05-02-0107-C {chrome} made for the Fat Bob for a Softail/Switchback, where I am using the Fat Bob Trees with the Street Bob legs and KW Wide Glide brackets. The difference between the FB and the WG version is the hole pattern used to mount to the lower legs. I don't think KW offers the brackets for the Street Bob per say, but the Street Bob and the Wide Glide use the same mounting points dimensions on the lowers.


So to answer the OP's question, with the use of the Klock Werks Fat Bob Brackets and the Fat Bob trees and legs, running a Switchback fender shouldn't be an issue.
http://www.getklocked.com/shop/front...na-super-glide


You can see in the pic where I had to do some trimming for my set up, again this shouldn't, <- key word, be an issue for the OP.

 

Also, IMO if you're going to add the longer style front fender used on the Switchback, you should also look into a longer touring style fender for the rear. I think it would keep the balance correct and look more natural.

 

Yes and I used a raw steel blank (Fits Softail) from eBay. Bought for $99. Paint with prep and all was $400. Would have been easier to find a switchback fender or softail fender. My adapters needed trimming like blueangel73 to make fit as well. Maybe mine were WG version as well-I don't remember.
Agree with Blueangel73 on rear fender. A switchback fender fit on my street bob without modification. I think a SB fender may work on the fat bob as well, I'd do some measurements before committing if you decide to go that route.

 

Not sure SW rear will work on a Fat Bob, much like the Wide Glide, those to bikes have a wider rear strut with wider rear tire/wheel, that is why I recommended a touring rear, specifically off an 08' or newer because they went to the wider rear end too. Unless he can find a touring blank that has no holes, he would have to weld up the exsisting holes and make new.