Motorcycle: 1985 GSXR 750, 1986 GSXR Limited, GSXR750RK (in restoration mode), 1973 GT-750 (no longer have, looking for another)
Re: Part for my slabside
Yeah, not much on a Katana would be direct swap and nothing would really be performance update. I'd pick up the speedo drive from the dealer. I picked up one for my 85 two or three years ago so I expect they still have stock today. Calipers can probably be had from the Classifieds on this site and you can probably get a line on anything else you're looking for as well.
Why do you want to lengthen the swing-arm? The 85 was slightly shorter than the 86/87 and is a bit more stable but lengthening it will affect the geometry of the bike.
I'm building a self-serve registry for listing our bikes from all around the world.
List your bike here: www.mcregistry.com