I don't know about a car dolly, would probably be about the limit weight and safety wise.
I have towed one with a tow bar with all 4 wheels on the ground.
[img]http://thumb9.webshots.net/t/58/458/3/29/25/2811329250080251109DYqOrz_th.jpg[/img] It worked quite well for the about 3,000 mile trip from WA to NY. However, I would not want to tow a truck that weighed more than my towing (lead) truck. Brakes and weight over the rear wheels of the towing truck are very important things to consider.
Grigg