Yep Ray is onto it, the stock systems have a sleeve clamp and most cat backs and dumps start and finish at this point, and the 42's can be ordered with adapters to suit the stock clamp, a 2.5" flange, or a 3" flange.
Guys it would be remiss of me not to point out the current Viezu Hardware specials that I can also now supply. I have not personally seen any of the gear, but the pricing sure looks keen. I am told the pipes are a few weeks away at this stage. I'll start a new thread with what info I have, and will put it all up on my site in the next several days.
So I've got till October 15 to save some pennys and I'll be ordering it off you,
3Inch sleeve style to slip straight on to my aftermarket cat back..
Might also get it coated up to the rear section just like your post yesterday.
I'll definitely keep in touch Greg thanks heaps.