Having completely overhauled and rebuilt a few freewheels in the 1970s, including holding the pawls in place with fishing line during reassembly (common trick on 1960s Regina units), I would rather just clean and reoil as described in this thread, even though this must be done much more frequently than the total rebuild.

cyclotoine: Your Regina has two or more spring-loaded pawls, one of which may have chipped or lost its spring tension. Before trusting it during an out-of-saddle sprint or climb, you may want to try opening it up.