Great improvement
I did a skid relocate a few years back to the exact same sled. Unbelievable improvement in deep pow. My son is still riding it. You need a 151" track, some 1/8" aluminum plate, and some 1/2" aluminum bar stock.
Fabricate the aluminum plate into a doubler that you bolt on to the outside of both sides of the tunnel. Mine was about 8x8 and conformed to the top of the tunnel and the running board. Drill mounting holes 3.5 " rearward and about .5" lower than existing. That is the front mount.
Drill out the rivets on the rear mounts (better yet grind off -they eat drill bits). Relocate the rear mounts 3.5" rearward and a about .5" lowwer. I used an aluminum spacer (bar stock) between the running board bottom and the spacer. Drill and bolt on.
Install the new track and enjoy an new sled.