I had an 01 800 that was my first brand new sled wasn't an LE. You can do a lot but it depends what kind of riding you plan on doing. The exhaust outlet plugs easily on that chassis in deep powder so a deflector will help that. Mine was geared down from stock since a mountain sled doesn't need to go 100mph. Also had heavier weights in it than what we're recommend on the clutching chart can't remember what I was running exactly. You can mod the steering post mount by removing it and mounting it on the front side of the support for a more vertical position. I also had a Holtzman Attac system on mine which worked great for compensating for altitude and temperature changes, it ran like an efi motor after I installed that. If you install a light weight can expect it to be loud even with the stock pipe. A SLP can was loud on that motor and they are usually the quietest. Make sure you don't run the pistons to long they are know to break the skirts off due to the engine geometry. I was told to put fresh pistons in ever 1000miles. I saw the pistons that were recalled on mine and it was just over 1000 miles at the time and they showed signs of wear on the skirts. I would keep the engine stock it makes good power and is reliable. You will also want to buy the pre-filters for the air intake grills. The position of the intakes causes them to ingest snow and freezes up your carbs. If you want taller bars a lot of guys put early m series or King Cat bars on these sleds.
Thanks man don't know abut the clutch I have can all ready and thanks for the info abut the pistons and where did u get the pre filters are u talking abut k&n filters and where did u get holtzman attac system from that would be good and I do alot of ditch banging and I do want to go to the mountains one of this days and what gearing is best for this sled