You should use a steel billet gear (get one from Ford Racing). The key thing for this gear is to set it properly on the distributor shaft for if it is too high or too low, the cam gear and the distributor gear will soon be toast.
Yes, you can use bronze gears but don't expect them to last a long time. You can't use a cast gear; the camshaft gear will eat it up quickly.
Last, don't depend on heresay, call Ford Racing and ask.