Dave
I take it you have the TKO II with the 3.27 first and .068 fifth.
The Superformance standard gear is 3.73 and I have the same TKO II transmission. In 5th at 65 it's about 2000 rpms which is great for just crusing on the highway. There is a gear/ tire calculator on the Superperformance/Second Strike website to help with your question. What's right is personal preference.
http://www.secondstrike.com/Technical/GearCalc.asp
With my 460 I don't feel the factory gearing is correct and I agree with MidOHasp. With 3.73's in the rear first gear is useless and 5th gear is almost a 1500 rpm drop from 4th. Next time around I will change transmissions to the new TKO 600 with a 2.87 first and 0.83 fifth with 3.27 gears. Big Blocks don't need all the gear, let the torque do the work.
Tony