Gentlemen,

Decided to upgrade my '68 with a 12 bolt differential with Posi. Bought a case and intend to have a local shop install the gears. I currently turn almost 3K RPM at 60 and because of where I live have to do a lot of highway driving. I've read some of the threads on gear ratios but wanted information on the driving experience for the various set ups. I'm considering 3.08 up to 3.55. My car is a "cruiser" so speed off the line is not an issue but also don't want a "slug." What say you?

 

Sounds like you have 3.73's. A 3.55 or even a 3.42 would be a good "all around" gear choice. Your tire diameter also comes into play to determine your final rpm's. I have 4.10's, and at 60 mph the engine's right around 3,200 rpm. A 3.55 would drop me to about 2,750, and I could easily live with that on the highway. 3.42 would put it around 2650. These are with my tire size, maybe not same as yours.