So earlier this year I decided to build a vintage bike for speed week 2015. I am finishing work on the frame, and all the carbon composite bits and pieces. I am down to the swingarm and am having a bit of trouble finding a suitable extension kit or viable swap for the bike. I plan on pushing the rear tire out 3 inches possibly up to four. Wrench tech racing at one point sold kits to extend the swingarm, but on every ocassion they seem to be out of stock. I contact them, but to no avail. If anyone has a bit of info for me I'd be greatly appreciative.
I had the swingarm on my CB350 race bike extended 2" by Framecrafters and the braced according to the AHRMA rule book. They just cut the swingarm and turned some sluggs and welded back together. It works great. I assume you could extend one even further if you braced it.
I will be around my cabin in the next couple of weeks if you want to come take a look at mine. It is 8 miles north of Menomonee on Lake Tainter, right by Elk Point resort. I think I will be there from about Dec 28 through Jan 2. I may have some other parts if you need them. I have a garage full of stuff.