Please help with G3R build

[suicideneil]

The only custom parts you will need are the center dogbones- most people would get Mike to make them to the length they require; the length will depend on how you position the centerdiff unit exactly on the lower plate of the G3r chassis ( custom installation that requires drilling 4 holes ). The only other thing you need is an actual centerdiff; ofna or hotbodies being the usual choices unless you opt for one of Mike's slipperentials.

Gearing will depend on the kv of the motor, the voltage you run & the size of the tires; you have BrianG's calculator to help you there:

http://www.scriptasylum.com/rc_speed/_top_speed.html

Differential Ratio: 2.8461538461538463
Transmission Ratio: 1
Other Ratio: 1
Spur Tooth Count: 54
Pinion Tooth Count: 9
Total Voltage: 22.2
Motor KV: 1700
Tire Diameter (inches): 5.9
Tire Ballooning (inches): 0
Motor Current Draw: 0
Motor Coil Resistance: 0
Spur/Pinion Ratio: 6 : 1
Total Ratio: 17.07692 : 1
Tire Circumference (inches): 18.54 inches (470.8 mm)
Rollout: 1.09:1
Total Motor Speed: 37740 RPM
Vehicle Speed: 38.79 mph (62.31 km/h)
Effective KV Value: 1700

As an example of the setup required when using the tekin 1700kv motor- geared for ~40mph on 6s lipo with stock talon tires. Not sure on the maximum size of spur you can use, its been discussed a few times- check the slipperential threads:

http://www.rc-monster.com/forum/forumdisplay.php?f=45

Often people use dogbones from other vehicles that happen to the the correct length, takes a bit of research, though BrianG again has a helpful page:

http://www.scriptasylum.com/rc_speed/_dogbones.html

Otherwise you could probably just use the stock plastic driveshafts form the erevo or emaxx, and cut them to length as required ( pair of longer ones and trim down ).