Well, first off I would not buy that truck you linked to. It would "work" but as soon as you started bashing hard or gearing up at all it would break and the sub-par electronics would fail. I would steer clear of anything but the big names in r/c, cheap knockoffs are cheap knockoffs.
If it were me, I would keep it and go the 3908 route. The 3908 gives you a solid brushless ready tranny, extended wheelbase and more room for lipo batteries. Your current front and rear ends are direct swaps.
Fastlane Machines makes a couple of really nice aftermarket 3908 chassis if you really want to bling the truck out.
It may be more money, but you will end up with a better truck, better electronics and the satisfaction of building it yourself the right way.
Here is a 3906 I upgraded to a 3908 with a custom carbon fiber chassis I made and a custom center differential instead of a trans. It also has LST diffs in the bulkheads:
http://rc-monster.com/forum/showthre...&highlight=pif
Good luck and happy r/c-ing!
