67 - 69 dart convertible

The differences between a hard top and a vert are too many to list. Windshield frame, rear interior body panels, quarter window and regulaters, rear wheel wells, on and on.
A vert frame has all 4 torque boxes that add strength but I really dont think they are enough support on a rotiserrie. I would add welded frame ties before mounting a vert on a rotis'.Good luck