final pix of subframe connectors

the floor pan and transmission crossmember in my 67 cuda is out of a 74 dart parts car. it had a 110" wheelbase same as your duster. my cuda is 108" wheelbase. i cut and seamed it together with my original floor pan at the back. otherwise they are the same underneath. the additional length is aft of the rear footwell where the inner floor pan boxes together at the start of the rear framerails, this is where i made the seam come together in mine. view my photos by my profile, i have a little slide show on how far i took it apart.

chassis wise they are identical except for the wheelbase from 67 to 76. im willing to bet my body rotisserie mounts im working on making will bolt in at the front and rear of your duster in the same place as my cuda does once you pull the bumpers and bumper mounts off. Ditto for dodge dart and valiant