I've been using the .82 as stated earlier with a 3.42 rear end. According to the gps at 70 I'm turning about 2450 with the same size tire 295-50-15s. Fith gear feels a natural extension after fourth without the large rpm drop or the higher revving when going from 5th to 4th. Here is a link for looking at different gears. I like this one because you can put any ratio you choose. If I changed anything it would be going to a 3.08 because I'm most likely going to swap to the MT SR Radials with my next tire change. They are a little shorter. If money is no object you could always buy a six speed and have both gears. Also with the 3.42 taking off in 2nd gear is easy if you aren't feeling running through all the gears.
http://www.classicchevy5speed.com/RPM-Calculator.aspx
http://www.secondstrike.com/Technical/GearCalc.asp