Ford Broncos are designed for rust. If your doors and tail gate are in that bad shape, I would pull up the rug in the back deck and check for other possible rust areas. Like ShadowD said, if you don't get rid of the rust. I have replaced a good bit ofmy 83 bronco's metal to get rid of it, but it is a yearly battle to check it out and catch new problems before they get out of hand. If you have a rust thru spot, the only cure is to cut it out and put new metal in. Infact if you realy want to have fun pull up all your rugs. The driver foot well usually rusts out due to wet rug syndrome.
I would take a good look at the door posts, anther famous rust out area. The rear mud guards are designed to allow mud and moisture to be thrown inside that area. I solved my problem by replacing post metal and redesigning the mud guards.
Good luck,
>-