Unless you are in the desert, I have never seen a Bronco that didn't develop rust-out in the lower tail gate section where the outer skin and inner frame connect. It is preventable, but FORD never took the time to do what is necessary to prevent it.
Also, the lower B-post area tends to collect dirt and moisture which causes it to rust out.
Other favorite rust areas are the rear corner of the 1/4 panels, rear body support member, driver side floor board, front fender wells where the outer skin and inner support connect (collects dirt and moisture), rocker panels, lower door skin where the skin and inner frame connect.
If you see a blister, you are looking at the tip of the iceberg.
Check out the body work pictures on my site below if you want to see where these places are.
Good luck on your quest and don't let a little rust ***** you, it is all fixable and depending on your psychology it might even be fun
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