Justin welcome FTE. A little more info would be helpful. Things like what truck you have. Engine size, transmission, stock or modified, what rear end, intended use, all comes into play when selecting a gear to make the most of what you drive and how you drive it.
If you run 235/75/15 tires you can get away with gear ratios as low as 3.00-1 but you start working it real hard at the higher speeds. My 61 uni had 3.89-1 with a 292 2bbl and granny 4spd and 31" mudders. It topped out at around 75MPH. It got 14MPG on a trip from Tacoma to San Diego averaging 60MPH with 1/2 ton of stuff in the bed.