Here are the side pics and more specific info.
The R6 Swingarm is longer, mine is about 22.75" from the swingarm pivot to the rear axle (this is tensioned, so its almost as far back as the wheel can go, about .25" left) and the min. adjusted spot is at 21" from pivot to slot. The total wheelbase comes out to 56" which isn't too bad, still turns really well.
I did not have to mod anything on the swingarm. i made a point to only grind away a the frame because this eliminates another source of error. The 400/600 mounting width is 8.75", and the R6 is 10. When you are doing this be careful because the 99-02 R6 swingarm is not symmetric, it is a bit wider at the chain side than the right. I took, off 0.625" off the right side because that is where it centered it, and then i cut away untill the chain side fit about (0.635") ". Also, after grinding down the frame, the pivot bolt for the R6 swingarm is (20mm diameter) much wider than the FZR one, so to make it fit i just went and bought a $24 20mm drill bit and drilled out the pivot holes on the frame so that i could use the R6 bolt and bearings.
Then the chain was another big problem, instead of making a new sprocket, i went to a salvage yard and found one in a big pile, looks like it might be off a quad or something no idea. it has a .25" offset, which was enough for this. i simply flipped the nut that held the stock sprocket and put some locktite on it to give it the most surface contact with the threads. after this the chain was hitting the clutch on the sprocket cover, so i went and bout .25" spacers and spaced the plate out as well as welded on a .25" extension on the clutch rod so it would reach.
Then the next difficult part was the shock mount, and that is something i didn't measure i propped up the wheel to where i wanted it to be when it was on the ground, and sized up a bracket to make it work, if you guy's need i could make a detailed drawing of it, its pretty nice because the placement was wedged in as far forward as the bottom of the top rail on the subframe would allow, so it would be really easy to make the same one and mount in the exact same place, assuming you have the stock FZR subframe.
there hope that helps a bit. let me know if you guys want anythign else specific.