vert700...you were right the first time. Just think about what is spinning (I like to think of it like a dirtbike)....the smaller the front tooth (top for snowmobiles), the more times is has to go around to spin the rear (bottom) gear....thus making it more responsive on the low and middle ranges. Also drops off faster on top. So, you were right the first time.
The other thing to respond to the original question is that the 2002 600RMK gearing (can't remember off the top of my head) would be a great starting point as it was a 136 that year (the last year that is was). Might be slightly higher, but like I said, can't remember off hand....