3 speed manual and 2.76 gears with /6

I'm changing the diff anyway since it is noisy and it has (1964) tapered axles. Just trying to decide and future proof, if possible, by getting the 3.23 or 3.55. It will be highway driven and the calculator says 28 inch tire a little over 2700 rpm. Should be good for 360 or /6. What do y'all think?