I've got some suggestions too...and I'll expound on GHF's post in bold.
I've been running GenII chassis since 2000 and have done just about everything you can to it...and saw what works and what doesn't work. Some things are gimmicks and some are NEEDED for this chassis.
RMK 800 came out in 2000 in the Gen II chasis with black hood and 136 inch track. The sled was a beast in its day and still a terrific chasis and motor. In 2001 the 800 RMK was still in Gen II and the Snow Check Special had the red hood and came in the 151 AND 144 track. Both 2000 and 2001 had the non exhaust valve motor.
I would absolutely do the following:
1) drop and roll (huge gains in powder can be made with a conservative drop and roll) Been there and done that.
2) different seat (I HATE going from my Boss hi-rise back to my Dad's stock GenII seat)
3) light weight hood (shave as much as you can from that front end)
4) ported track (jury is out on that...you can definately do this one wrong and have problems but it can also be done correctly too)
5) rear skid drop brackets (drop the front mount too when you do this)
6) rail extentions to accomodate longer track
(IF THE TUNNEL is long enough)
7)
8) big wheel kit (rolling resistance lessened somewhat)
9) extravert drivers (lets you run the track a bit looser with less rolling resistance)
10) cylinder porting or high compression domes (the non-ves motors NEED porting. The casting from the factory is crappy and porting is slow but don't get too greedy on the compression.)
11) hyper fax (I would ALWAYS put these on. They are rated a lot higher temp resistance)
12) light weight front suspension--spindles, shocks, rods and t-arms.
I did all of those to my sled and have had GREAT LUCK with those types of mods on that chassis. That chassis LOVEs those types of mods.
OR if you can spend less on all that stuff and buy my sled that listed in my signature...