Yes it would change your gearing (make it taller). You could do it with out going to 8" wheels on the rear, but may run out of track tension adjustment (shorter) as a 8" driver is a pretty big jump in size.
The main issue I could see would be track to heat exchanger clearence, probably would have to run a very short lug track or remove the front heat exchanger and add additional heat exchangers else where.
In the end, I'm not sure if it would be worth the extra work. Unless you are building a full custom chasis and are "starting from square one".
http://fourstrokesolutionsllc.webs.com/snowmobilerelatedtech.htm
Bill
Snowmobile driver diameter specifications
2.52” pitch drivers inches Metric (rounded to nearest mm)
10 tooth 8.021” diameter 204 mm
9 tooth 7.219” diameter 183 mm
8 tooth 6.417” diameter 163 mm
7 tooth 5.615” diameter 143 mm
2.86” pitch drivers
8 tooth 7.283” diameter 185 mm
7 tooth 6.373” diameter 162 mm
3.00” pitch drivers
8 tooth 7.639” diameter 194 mm
7 tooth 6.685” diameter 170 mm
Changing driver size will also effect over-all gear ratio. For example when changing from a 2.52” 9 tooth driver to a 2.52” 8 tooth driver. You would multiply your 9 tooth ratio by 1.13.
Example: 20/40 gears with 9 tooth drivers would be 2.00 to 1. When switching to 8 tooth drivers with the same gear set the new ratio would be 2.26 to 1. (2.00 x 1.13= 2.26)
Note: the 1.13 multiplier only applies to 2.52” pitch drivers. Although the 2.86” is fairly close to the 2.52" and could be used for a 2.86" driver to get a general idea of ratio change.