I have a classic truck, a 56 Ford with a 5.0L H.O. and a C4 Automatic. I don't know what the donor car was for either one, but it's obviously important that I maintain them. So, while I understand the recommended ATF was likely Type F back whenever this transmission was manufactured, I am wondering if any of the more "modern" ATF's available on the market today would be recommended. Is it better to stick with what was originally used? Any input is appreciated.