what kind of transmission is in my truck?which vehicles are interchangable?

There are 3 choices on transmission possibilities on your vehicle. Ford used the 4r55E and 4R70W for their automatic choices that year and also offered a manual transmission the M5od-R1. To be for sure I would need the VIN number to help you. Also just a recommendation, Its always better to rebuild the transmission unless it is damaged beyond repair. For example, Yes the transmission might be cheaper but you have no history on that transmission and there is a very big chance on contamination in the unit. What kind of issues are you having?