You might have a tough time with those larger tires. The MT2 diffs certainly aren't the strongest out there, and any tire over about 4" tall is going to stress out the diffs. My MT2 is the 18SS kit with the hardened ring and pinion gears, and even still they would click with enough torque running Proline Road Rages (2.2). This was fixed by getting some aluminum differential housings (reduce flexing between ring and pinion), but I'm not so sure aluminum diff housings would help the stock non-hardened diffs.
But if you do have 18SS diffs and aluminum diff housings, then you're at least on the right track. Badlands 2.2 are 5" tall, and the Savage tires are at least 6" tall. With Badlands and 4s Lipo and 40mph top speed, you need a motor with a kv of about 560. On 6s and Badlands for 40mph, 370 kv. Savage tires + 4s Lipo and 40mph requires a motor with 460 kv. 6s and Savage tires at 40mph, 310 kv.
You can of course go faster than 40mph, but the motor needs to be sized appropriately. I wouldn't push a 2826 faster than 40mph, but even the slowest of them (2826/12) has a kv of 760, which on 4s and with the Badlands tires would result in a theoretical top speed of 55mph. That pretty much means you need to bump up to a larger motor, which would be the Axi 4120 series:
http://www3.towerhobbies.com/cgi-bin...RCH=AXI+++4120
These motors have more suitable kv ratings, but even still might be a bit too fast based on your choice of tires and voltage. For Savage tires, the 4130 series would be best:
http://www3.towerhobbies.com/cgi-bin...ARCH=AXI++4130