The tracks and drive axle are the same. I have 79' and 81' Invaders, and the ride on the 81 is noticeably better. I have a gas shock on mine and it rides very nice. If I were in your situation, and was planning on putting some trail miles on the sled, I would make the swap. I also recommend upgrading the track at the same time. I put a 1" camoplast hacksaw on my 81', by far the best mod I have ever done to a Kawasaki.