I tried finding a gear diff setup, but unfortunately I had no luck - if you wanted to go crazy power, that is what I would recommend
I have found that the evader is a great truck and stands up to some major punishment. I have had mine for nearly 10 years and the diff is the only thing that has really let go on it - and that was really my fault for putting a 5.5t in it for laughs.
Good luck and have fun!