Look around ebay, there are various divorced t-cases that will work, ive used an axial transmission on my 6 X 6 as the T-case. If you want to keep the stock rear axles I believe the best way to go is the TLT steer axle. I didn't have an issue with it being wider, guess I didn't notice it was. There are some all wheel drive options out there if you want buy all new axles.
http://www.rctruckandconstruction.co...ead.php?t=9138