I would contact Remco, Store : Remco
. They make transmission lube pumps, drive shaft disconnects, etc. They will be able to assist you. My 2004 GMC Denali All Wheel drive required a transmission lube pump, my 2008 and 2014 Cadillac Escalade full time All Wheel drive can NOT be towed 4 wheels down.
Have you considered a trailer? Trailer will allow you many options on taking any vehicle, no damage from road debris, clean vehicle when you arrive at your destination, no getting wet when hooking up your car when it rains. Biggest drawback is when taking coach in for service, unless they allow you to leave the trailer. It takes maybe an extra 10 minutes if you must unhook your trailer at RV Park than towing 4 wheels down, but much greater flexibility.
Towing 4 down isn't just purchasing the tow bar, it is the base plate which usually requires cutting holes into the plastic from grill/bumper, auxiliary braking, and lube pump/etc.
Just food for thought, I have done all methods of taking a toad, the past 2 years I love the flexibility of the trailer, there are times I wish I still had a vehicle for 4 down towing, but I don't have that luxury currently of having both options. Good Luck!