Hey guys i have a 1990 dodge dakota with a 3.9L and a three speed trans out of a 1989 Dakota. i think the rear end is the original from the 90 dakota.. its a 3.90 rear end. what would be better for the highway? i need a rearend that will give me better top end on the highway. thnx guys!

 

A numerically lower (ex. 3.55 vs. your 3.90) would deliver better fuel economy, but worse acceleration.
How much, I don't know. There may be calculators out there you might be able to find.