I just replaced the trans in my 2002 F150 and went with a factory rebuilt that has a 3 year unlimited warranty. They provide a new torque converter and replace all the electronics as well which other rebuilders don't. You would need to provide a VIN to find the correct transmission for your truck. Check out Ford, I wish I had known about their program when I had the last one rebuilt (crap).
Modern engine and transmission compatibility is complex due to the electronics involved. It is best to use the exact correct trans for your truck.
If it is a 4 speed it's probably a 4R100. But be careful if using a tranny from a donor vehicle. The electronic/solenoids and torque converters are very expensive, and if they are defective out of the donor vehicle, you're going to be wasting a lot of time in installation. If you've owned the vehicle since new, or know it has not been dogged, I suggest you have your's rebuilt by a qualified mechanic or purchase one remanufactured by motorcraft. As "Full" stated; three years of warranty is a good deal.
Something else to consider. Speaking to a Ford mechanic it look up the rebuild time for a 4R100 transmission. It's almost 13 hours. An install of a remanufactured transmission is a lot less. What you're saving on labor costs can go toward the purchase of the transmission.
Looking for a Used F-150 in your area?
CarGurus has 193,348 nationwide F-150 listings starting at $290.
Search Ford F-150 Questions
Ford F-150 Experts