[Bigdually]

Aside from the noted lower flat hump in the floor, the firewall is different. Not really sure how much massaging it would take to get a one ton front clip to fit. As far as cab mounts go, I may be wrong but from a quick glance they appear they're the same as a c10-30 cab, the medium dutys use tall bushings to make up for how high they sit above the frame.

Note too that all year square medium duties have the dimmer switch on the floor and wiper switch on the dash like the pre-83 pickups and unless the truck was optioned with the big back window, you'll have the small back window. The sheet metal surrounding the window hole on the mediums is different than a pickup, so to install the bigger window is more involved than simply cutting out the stamped hole and slapping it in.