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!!
Oh yeah... welcome to the forum...
Alien