Since you don't have that information:
* Consult a Repair Manual: Obtain a Haynes or Chilton repair manual for your 1996 Ford F-150 with a 302 V8. These manuals will have the specifications.
* Online Forums: Search online forums dedicated to Ford trucks or the 302 engine. Someone there may have the information. Be sure to specify the *exact* year and engine.
* Auto Parts Store: Go to an auto parts store (AutoZone, NAPA, etc.). They can look up the correct spark plug gap using your vehicle's information. They may even have a chart.
Important Note: The gap is crucial. Too wide and you risk misfires; too narrow and you risk damaging the spark plugs and ignition system. It's best to get this right. Don't guess.