[sassgrunt]

Bret is absolutely right about not just having the axle to consider, Jeff. Along with a transfer case that allows both ends to be driven, you'd also have to decide on how much articulation you wanted (which leads you into a whole other world of complexity), and also you'd have to make/modify/buy drive shafts that would fit. Sorry for oversimplifying all that.

I've done a couple of these in the past, and for the money you'd need for the parts (as well as all the head-scratching to get them to work together), if I had it to do again - I would vote for the Cross. RC4WD has had some sales in the past for their kits, and that might be worth watching. Also, Ali Express has kits that are usually cheaper than elsewhere. And, you could always substitute a fifth wheel for the bed, (by screwing a plate to the frame and the fifth wheel to that). There are even aftermarket fifth wheels now that can rock from side to side, and not just fore-and-aft like the stock Tamiya ones. Would help with something you intend to take off road, hitched to a trailer.

A few people have converted the plastic Bruder flatbed into a tank transport trailer. Usually involves lengthening the bed a little and changing the kingpin to something that will connect to an RC fifth wheel. But, they're not very expensive; even if you wanted to splice two together to make a longer one.