Excited! You have your upgrades right. Way to go. My suggestion as you are asking would be truetrack arms from RPM. And castle creations for the electronics. Hyperion for the batteries. A true truggy body is in order as is a wing.
Nice score on the truck! How long have you had the chassis? What is your experience with the Maxx?
-Zack
Wow... this should be a nice project... they are two sets of supermaxx diffs on ebay now, maybe you can have a look at those... what about adding Mike's Universal Center Diff/Motor Mount?
a CC 1518 or 1520 would power it really well.... the Racebomb is still my most favourite maxx kit... good find man... post up some pics!!