He would do fine BC they were on average hittable brawlers with less outside boxing who were around or under 6'3 . Where he actually would rank is anyone's guess BC he hasn't fought the relevant fights yet. His overall skill at 6'7 and power put him in top 5 just like today. He has major holes that can be exploited but he's still also realistically a 6'7 fast power puncher a threat in any era just BC of that, one punch is all it takes and he would land a lot of them against guys like Quarry, Shavers and Lyle.
He wouldn't be undefeated and would suffer a few losses by stoppage, but Ali fought a lot of great fighters, who would be killers in any generation.