I,d have to say EVERYTHING. When I bought it. EVERYTHING just about was tore up. All underneith was replaced , It seems like every time you go to repair something. You will find something that needs taken care of. These BRONCO are like ALOT of women--NOT ALL. Seems like they keep a person broke.
Well... I'm in the middle of installing my full roller C6 and twin stick NP205 rebuild. I hope it's worthwhile! I still have thrust washers in positions 4, 2, and 1 (selective), but torringtons everywhere else. The NP205 needed a full rebuild anyway and the Bronco is being built with off-road prowess in mind.... so I figured "Why not do a twin stick?".
While I expect a noticeable improvement, I don't think it will be anything like the rebuild of the 400 and having 350+HP under the hood.
A set of seats out of a Ford Escape. Cut up the factory bucket brackets welded them to the Escape brackets. Passenger seat now slides forward and back and still flips forward. Paid $20 plus tax for the pair.