I'm obviously doing a lot more to this truck, but changing all the body mounts CAN be done with the body & core support in-place. Loosen the bolts on ONE frame rail and use a 4x4 & jack under the door to lift the body enough to work. If necessary, disconnect the steering intermediate shaft and (Bronco only) the fuel filler neck. If a pressure washer isn't available, dental picks & a shop vac will also work to remove the rust packed in the front mounts.