I consider my sled a mountain sled now, it is an indy 650, stock they are trail sleds. I got a mountain tunnel on it and long track with 2" paddles, and clutching and a few other mods. I would post pics but I dont have a scanner or a digital camera though.
I converted my 2000 doo Formula Z 700 to a mountain sled. It has a Expert X 136 set back 4" to accomidate a 144 X 2. The engine has RKT heads with domes for 8500 ft and above, Cudney pistons, Holtzman ATAAC, DYNO Port pipe (Ceramic coated stock shown in pics).
I did purchase a boss seat that is not pictured. I have to install it when I get my sled out of storage.
I am also contemplating buying a Hyper Lite Roller Secondary!!