Do you know for a fact that the engine is originally from a Bronco? Or whether it's had any swapping done in the front? Timing covers, dampers, radiator outlets, all can have an effect. Unfortunately, Ford probably used 3 or4 different setups, not even including the later Explorer one with the crank position sensor integrated into the pointer.
Can you see a pair of small threaded holes anywhere around the circumference of the damper ring?
Oh well, at least if it's properly set up for your Bronco, it should at least be easy to mount once you find one.
Good luck.
Paul