I see a few Vincent powered FB framed bikes around from time to time, and there is a guy locally who was one of the original members of the Oregon Vintage MC and he has a nice one, its been featured in a few places as well as several newsletters. I have pictures of it on a memory stick in my office buried somewhere.
I knew a guy called "Hack-a-saw" in North Carolina about 15 years ago building a Mongrel FB framed bike with a BSA A10 Tranny, A HD 45 motor and FB frame,, He called it a "Hard-on" and said it was "Fast in the corners & slow on the straights" and planned to eventually build it as a Magnum 45 (Ironhead sporty 900cc top end and other hot rodding,) But last I heard he got a divorce and sold off many of his collection & projects.
**(PS, If anyone wants a good tech article on HOW to build a 45 magnum PM me, I am scanning one for a friend who is building a Magnum)
But there was a guy locally who got some press for a "Norley Fartster" with an Evo sporty motor and I thought he did a great job. At that time I had been out of the HD scene as it got to embarrassing,, but a friend left me his hot rodded Evo Sporty for 2 months and the wheels started turning with a Tape measure and I told him he was lucky he was getting his bike back in one piece. I got back into Sportsters and Buells at that time.
Since then, several companies and builders have came out with their own HD V-Twin compatible FB frames,, Before Unity Equipe in the UK closed up they had some wideline frames for sale, and a few other vendors were offering some too. There is a shop in Florida USA offering them as well, and another shop that offers cafe racer stuff is coming out with a frame as well.. NEW Manufacture setup for Sportster, Modern Triumph or engines of your choice. Most slightly lengthen the Wideline frames and because of the cyl heads they need to be a wideline, not narrow line. (EVO sporties are 1 to 1.5" inches taller than a Ironhead) But there has been some built using Big twin HD motors too..
Cafe racer magazine (Editor is Mike Seate who wrote for a number of magazines over the years) is a US Magazine that has a lot of promise but some technical issues in some areas, but they have featured some nicely done cafe racer Featherbeds including several with HD motors. I have been meaning to subscribe but have not yet, but its been 6-8 months since I last bought a newsstand copy but they attempted to build their own magazine feature bike (Features of the build over several issuse) and they made some unfortunate coloring and styling choices that went badly and they were retooling. But I believe they ordered a new frame from the UK and featured one of the UK builders. I can dig out the issues if anyone wants the details.
I do not wish to diminish the coolness of this bike that started this thread. I like it a lot,, but most of us mere mortals will never find or be able to afford to build something so cool, But HD Sporty and Buells are extremely affordable here in the US and make excellent cafe racer donors. So.. I am attracted to them for many reasons. (Love building customs as well as resto)
Here is a picture of the Florida companies Norley platforms and some bikes they built. (LOADS more where that came from) (I have a LOT of Norton stuff so kinda in my wheelhouse)
But< I admit, to a very great deal of admiration of a very cool London UK based shops race bike in a featherbed,, Its a KR750 based HD race bike in a FB frame and similar type of fairing as my avon aire fairing so while I was leaning towards a typical Silver/black paint job with de rigueur red/black striping for Norton race bike colors, The Orange and Black look stunning on this one, (I have some really cool Supertrapp stainless race bike waist high exhaust for the project so, it would look great to complement the look)
