Getting the centerline above the chassis you are gonna run into driveshaft angle problems. The driveshafts will rub the chassis if the diff is too high.
I just learned the losi 8ight 2.0 center diff has a plastic spur that comes in 43 tooth. Maybe that will be the answer.
Get a measurement between chassis rails, then you can use BrianG's app to know the diameter of a particular gear. It shows a 43t spur gear is 45mm wide.
app here >
http://www.scriptasylum.com/rc_speed/gear_calc.html