I bought a kit of an Avalanche for my ext cab Sierra.
Couldn't use any of the hot or cold side tubing under the truck. Had to make every pipe from scratch..............

 

It looks like they mount it WAY back there. I dont see why it would have to be mounted back there. I guess I'll install it from the front back and see where the small pipe crosses the frame and measure from there to the Y and lengthen or shorten as needed. I would rather it be mounted as far forward as possible anyway. Any reason why that wouldnt work?? The front compartments and Y are the same on my truck as on the Ext cab correct??? And it looks like there are several points in that area between the body and frame to cross over.

 

I was going post pics of my truck but they are allready up. lol

 

After looking at those pics, it looks like this may be a little more difficult than I thought. Everything is different. Looks like the pipes run inside the frame as opposed to crossing over it. Looks like Im going to have to take some time and mock things up. Does the frame to body clearance lessen with excessive suspension travel? Is it possible that the piping could get crushed? Perhaps thats why the piping doesnt cross over the frame on the AV and Tahoes?? Im going to mount the turbo as close to the Y as possible and I guess I will see what can be done with the piping I have. I can see why the AV/ Tahoe kit would not work on an Ext cab as it mounts it so far back and wouldnt work with the truck suspension back there. I dont see any reason I couldnt the turbo where the muffler is now??