how much difference between 3.91 and 4.10

I think im going to probably end up with 3.91's....My car is minitubbed with quite a decent sized tire under it, so if i want the acceleration im looking for im going to atleast need a 3.91...from what i am reading, the 4.10 although not much different seems like overkill for the highway

With your tire size at 70 MPH your RPM would be with gears:

4.10 = 3506 RPM
3.91 = 3308 RPM

That's only 198 RPM difference.