I agree what Saban is doing is much more impressive than what anybody did pre-1992 (when they imposed the 85 scholarship limit). Before 1973 it was 150 scholarships allowed. From 1973 till 1992 it was 105 scholarships.
Also, when you consider that pre-1998 teams won national championships by having different entities vote on them. When you consider all that, Saban is the best head coach in NCAA FBS history.
If you want to go down to Division III. You got Larry Kehres, who went 332-24-3 at Mount Union. He has more seasons as a head coach than he does losses.