About 3 years ago I bought a frame and firewall back tub (with roll cage), rolling on gutted and hollow axle tubes for $500 I then sold the tub for $515 on ebay, sold the axles to a friend for $75, sold stock radius arms, coils, and leafs for $50....So basically I got a frame for FREE and was as if someone paid me $135 just because....the cage was pretty shotty so I just cut out anything worth saving and took the rest to the scrap yard.
The only down side to the frame was someone welded MASSIVE 4x4 inch steel blocks to the side of the frame to bolt the roll cage too. It worked pretty well, but were a pain to remove.
If you have the time and space, parting out a Bronco can be pretty profitable.
The frame I have since been working on fully welding, flipped the rear shackles, added brackets for extended radius arms, plated and gusseted steering box, and planning to move the drivetrain back about 4 inches.