Someone who really knows please step in and correct anything if needed.
IIRC in various threads about this subject, Ford (USA) never made a RH taillight bracket. LH only. The stock rumble step bracket is not compatible with a mirror image of the LH bracket. There were many period aftermarket taillight brackets, some cast, some stamped, some compatible with the rumble step bracket (some not), and some designed for a rumble step. So anything goes.
Ford may have had a RH bracket but marketed to countries with RH drive. No definitive answer.