I always thought that tow dollys were for towing front wheel drive vehicles without having to disconect the drive axles. With a heavy truck such as a 6400, I think that it would be safer to keep both axles on the pavement.
I would build an extra heavy duty tow bar. If you have working brakes in the 2 ton, you could have someone ride in it to assist in stopping. You could communicate with a set of inexpensive walkie talkies.
Unless of course there are mechanical problems with the front axle.
