Can't believe I missed this thread. I have been going down a similar road; picked up a D700 with a 360 AT and very large Rockwell rear end. Wanted to make a car hauler out of it as well but somewhat stalled. I am have issues with the brakes and finding parts and information is a pain. When I got it, the brakes somewhat worked but found out that the MC was leaking, after a lot of research I found a replacement as the same "type" of MC was used on IH school buses. Got one, then the front brakes began locking up. Called a guy in MA who is knowledgeable about Dodge chassis (think motorhomes) and he tells me that the MC is unique to Dodge even though every book cross references the IH part and that it will not work. Well, since I had already dropped $200 on the MC I took it apart along with the old one, they are identical internally. I know think my front brake issue is something else that resulted from when I actually filled up the fluid; something like the wheel cylinders sticking out (when you touch the brakes, the front grabs hard and doesn't release, but will over time). So now I am thinking it needs new front wheel cylinders (2 per wheel) but are one sided and I am having problems finding them. I think that a normal 2 sided wheel cylinder kit of the same bore diameter will work but am not sure.
Other issue relative to making a hauler is how to get the bed low enough to load and unload it. Will have to be a tilt bed.
