I think Charles would pick Bonavena apart and give him a pretty severe boxing lesson, winning a UD, and maybe scoring a knockdown or two ala Ellis.
Charles by decision, but he will not dominate. Bonavena has a punchers chance though and might knock Charles down during the fight.
The best Charles (even the one after killing Baroudi) would win against the best Bonavena viĆ” lopsided UD, ca. 12-3 rounds...
The key here would be the mobility and counterpunching skills of Ezz, who was very adept at boxing on the move. Ringo needed to get himself set to be effective. In Jimmy Ellis's peak performance, he proved that Ezz would not be too small to inflict substantial damage on Bonavena. Oscar lasted the distance with Ellis only because that match wasn't scheduled for 15 rounds. Charles might have to climb off the floor to do it, but he would get Bonavena out in the championship rounds. Oscar would simply leave too many openings for the clever and fluid Charles to exploit. Charles TKO 14 Bonavena
Charles schools him no problem Foley and Ellis outboxed Oscar,dropping him along the way Charles was better than either of them.