Use the link pipe for your headers with a 3TJ hybrid Kris. All of ours (I think we've done six now) have used the headers for the engine and the link pipe to suit. It's a really tight squeeze under the right side of the frame but the 600 parts fit on the 400 chassis. Don't use the EXUP system with the 600 engine, they (600s) never had one fitted as standard and it's just easier to use all the 600 electrics with the 600 engine.

The standard 600 (FZR and Tcat) systems have a 45mm exit on the headers for the link pipe.