Hy dejmeister, welcome, when you ask questions please remember to tell us as much as you can about the vehicle you're asking about, that way we're not just guessing blindly. As OldSub has said GMC trucks of the 50s were only equipped with a Hydra-Matic automatic transmissions from the factory [the same is not true for sedan deliveries]. Some Hydra-Matics were water cooled, but more were not. Try to find and post your serial number, a lot of information can be gleaned from that, to identify both your truck and its original equipment engine, hope that helps.
