Quote Originally Posted by rumrumm View Post
I agree with Dave. A set of 3.25 gears will give you the best cruising rpm. You should have enough torque with that big block to get you off the line and provide you with good performance. Everything is a compromise. An overdrive gives you more flexibility--I run 3.89 rear gears with 30 inch tires but I can cruise around 2200 rpm at 70 mph.
Like Lynn, I run 4.11's with 31" tires, but in 5th (0.64 OD) I cruise at 2000 rpm at 70 mph. You'll be at ~2535 rpm with 3.25's, which is pretty good if you're not looking to change to an OD unit.