jsut a refernce point, my boss has a 3/4 ton chevy with the tbi 350 in it, and according to uhauls standards, the weights are too close for it to pull an auto dolly with a toyota on it....
my friends f350 4x4 crew cab however is advised to pull the yota on a dolly or flatbed trailer
i personally would not tow doubles with just a 1/2 ton anything.....