Hi
i had the same question about 210 gearing this is what i found
According to Novak the recomended gearing for a 2wd buggy is 9.5
http://teamnovak.com/tech_info/view_article/26
if you then look at this
http://www.petitrc.com/setup/durango..._GearChart.pdf
notice the spur only goes to 87 which is std, if you get 87 or smaller spur it will move the motor nearer the rear axle
another problem running a bigger spur is that you may not have room to get a big enough pinion on