I have done this to my 08 TNT and am now working on my wifes 09 TNT.
On both of them I have moved the skid to the rear (front arm tunnel holes) about 4.25 inches and then make up the rest of extension with extension plates.
The wifes TNT am using short extensions about 4 " long from Tracks USA. Her sled is getting my old 16 X 137 X 1.75. You can now get this size track with 2" paddles I believe. This length track is right on the edge of still getting some cooling from the snow kicked up when the track comes around the rear axle so it hits the heat exchanger.
My sled is about as mod as you can get without a turbo. I just put in a camo (cat replacement track) 15 X 141 X 2.25 and it appears to have some cooling issues now. Snow is missing the exchanger in the rear so may have to get longer upper coolers (renegade) or move the shortys back to the rear bumper. Now my sled only weighs 365 lbs and part of the way I did that was
by deleting the front heat exchanger (4 lbs.) and I got away with it fine before the longer track with bigger paddles. This even though mine is big bore 629 and piped, high compression head, ported etc.
The link to the thread above is my sled and covers pretty much everything I did.
Oh yeah I move the skids back to soften the angle of attack so they act like a mtn sled and don't trench. My sled is amazing fun in the powder!!!!!!
Good Luck