Would probably be a very entertaining fight the fight would certainly go the distance with Whitaker winning a wide UD. But Augustus would have his moments and win a few rounds.
Augustus developed into one of the best journeymen of the last 30 years but make no mistake, he was still a journeyman. Those 30+ losses, he wasn't robbed in a lot of them, he just wasn't on the level to compete with the winner. And he'd be up against someone far more slick, faster and offensively gifted. Pernell would make Augustus look silly. A journeyman can and will make some guys look bad. I've never really seen Sweet Pea look "bad" in a fight aside from his last one (Tito you can say he did, same as with Hurtado but he was literally on coke for probably those last 3 years)