So I got two NOS Kat 600 calipers and an NOS Kat 600 front master cyclinder all for $60 on eBay! I priced them on bikebandit.com and they cam out to $605! We're talking brand spankin' new with all the plastic plugs still in place. This is perfect for my Kat front end swap. Put them together with my galfer braided lines and EBC rotors and I've got a zero mile front braking system. I'm not sure if the guy has anything left that any of you would be interested in, but the eBay ID is armytad007 and the business is Anderson Vintage Parts. They're clearing out most of their newer NOS inventory to make room for more vintage stuff. They've got brand new body panels for Kats and Gixxers. Lot's of varying engine parts. Unfotunately there aren't any GSF400 parts, but it's all Suzuki.
John