Hi there. I have a 56 f100 with the stock 272 with the stock 3 speed manual transmission. I want to replace the tranny with an automatic either an original automatic ( which I hear are very hard to find) or a newer auto transmission. I want something that will bolt up with no alterations or very minimum alterations. My reason for doing so is because when I drive at about 40mph in 3rd gear it sounds as if im revving out already. Wil a 4 spd or auto change this or is it something that I need to change the gears out or both? but either way in the long run i would like an auto tranny. thanks guys any help would be great