I have a old 1971 ford f250, witch is great other then the gearing is way to low. On the highway going about 55 the rpm is around 3200 and at 80 I think its 4000-4500 when its in 4th gear. I don't even use 1st gear at all cus its so slow. The diff ratio right now is a 4:1 I would like to be at 2200 rpm at 80mph in 4th gear but can't find a clear answer as to what I should change the ratio to.
Added (1). I typed the question a bit fast, I mean what would work best that well allow me to travel on the freeway comfortably.
Added (2). sorry the ratio is also 3.25
Read more: https://fordnews.org/duty/what-should-i-change-my-diff-gears-to-for-highway-use.html
