I have the 3.73 with 30 in tires great gear compared to my brothers 3.42. I'm currently having them swapped to 3.90 and going to a 31 in tire for the street and 28 in for the track. In relation to the 30 in tire with the 31 in the 3.90 should be the same rpm/mph as a 3.73 and the 28 in should be the same rpm/mph as a 4.10. Go with the 3.90