Planning a 440+6 tow vehicle, need a plan

You have to look at the GVWR. Even my D100 has a pretty low rating, like under 7,000 lbs. It's a SWB with a 400. The engine is not the issue but since it's a SWB, it's not meant to tow big stuff and if you look at the chassis specs, it's lighter duty than a LWB, even with a 318.

The truck itself probably weighs 3,800-4,000 lbs and with my Duster (approx. 3,100 + trailer approx. 1,500-1,700lbs.) I would be over the GVWR. I plan to tow with it anyway and I think it will be OK but it is pushing it.

The point is, an A body 'Cuda probably has a pretty low GVWR so even with a lighter trailer, you'll still be over the limit. The chassis is really not designed for towing.