honestly you would probably be better off auctioning the one off as a roller and buying a used 1/8th buggy, truggy, or even a savage(if you want a Monster Truck) roller and putting the radio, servos, and sirio motor in that. Instead of trying to reinforce the XTM's diff. Trust me trying to fit diffs from other vehicles in can get expensive fast been there, and done that.
but thats just my opinion