Not an A Body question

Check on weight distributing hitches. I don't know how much that would help, but I know they add to the total towing capacity. Also check overload or helper springs. If you're gonna try to increase the towing capacity, make sure you have a good external trans cooler. I personally think every truck should come with a trans temp gauge. I'd like to put one on my Ram one of these days, when I can quit spending on the Dart. That may increase your capacity by 500 - 1000lbs. But I guess your mileage may vary.