Towing a Car Trailer

The tongue weight and total load are going to be the lesser of of the class of hitch rating and the vehicle capacity. Many new cars and smaller cars have no recommendations for towing whatsoever, and my general rule of thumb for pulling trailers with no brakes is to keep the trailer less than half the weight of the vehicle, and the tongue weight no more than 10% of the trailer weight. So your average passenger car can pull under 1200-1600 pounds max, with a maximum tongue weight of 120-160 pounds.
This is what I found about your SUV online:

Engine: V6, 220 HP
Gross Vehicle Weight Rating: 4,950 lbs. GVWR
Max Trailer Weight: 3,500 lbs. towing capacity.

I'd say you could pull a 70s Dart short distances with a tow dolly, but you're at the limit. Really, it'd asking a bit much out of the vehicle.
A mid- 60's Dart like yours is lighter, and a trailer with brakes would certainly improve things. But the weight is still pretty high. Are the roads flat, or will there be hills to cross?