Strong Lead isn't that uncommon. Many fighters have done it both directions such as naturally left handed Cotto and Delahoya fighting orthodox and naturally right handed Pacquiao fighting south paw.
'Converted southpaw', as in converted from southpaw, refers to a naturally left-handed guy who boxes in an orthodox stance, which ideally results in a strong jab and/or hook. Miguel Cotto, Oscar De La Hoya, Gerry Cooney, Ray Mancini. The opposite of that (as per the OP) could be called a 'converted orthodox' fighter. Winky Wright, Mike Moorer, JuanMa Lopez, Vic Ortiz (remember that sweet right hook-right uppercut combo)?
Didn’t know pac was naturally right handed? If that was the case why did he have a poor right hand and a devastating left earlier in career?
I used to turn south paw once in awhile and my trainers would hate it, freakin short sighted trainers hate change to often. Mind you i was always getting my head punched in so maybe they had a point. Then again, i wouldnt do it for long, i would only do it when i had OVER USED my left jab without being able to throw many rights. Thus if my right was super fresh instead of going head hunting with it without a fresh jab i would turn south paw for a breather and eck out part of the round using power jabs from the south paw stance. I personally remember it as helpful as if i was in a jab fest it was a great way to rest my left jab just enough to keep it fresh.