Guillermo Jones a prime light middle ended up becoming a really good cruiserweight and a heavyweight. Dingaan Thobela was a prime lightweight ended up world champion at super middleweight. Epifanio Mendoza was a lightmiddleweight contnder who ended up becoming a dangerous heavyweight journeyman who caused some upsets
John Conteh one of the few to do it in reverse. Started off a HW and Ali told him he would be better at LHW. And ended becoming WBC 175 Champ.