Which Gear?

Agree, if it is one the highway more than 30% stay with 3.55 max. Maybe a 3.73 with a taller tire. My truck for example has 4.11 but the tires are over 32" So the correct thing is calc the tires & gears to get the real RPMS at 60-70 mph. I would say try to stay under 3k at freeway speeds if it is a highway car.

I used to run 4.10s on a 24" tire in my Dart for a time. it was in no way a highway car. I recall 4k at 60, car overheated etc. on a long trip. So 3.91 would be iffy even with a 16" tire.

Cant have it all without an overdrive..