I didn't see much different between the forthcoming Revell Baja Bronco and the existing Revell Ford Bronco kit, but after looking at enlarged images, there are a few noteworthy changes:
Hexagonal wheel arches with integral fender flares
New tires (anyone recognize them to be a replica of a real tire?)
Newly engraved nameplate above the front side marker lights(?)
Instruction sheet is up and downloadable: http://manuals.hobbico.com/rmx/85-4436.pdf
Pics of the new Baja Bronco and the existing Ford Bronco, for comparison: