I would imaging an easier way to go about leveling the front out would be to put coil spacers.
But if you want to go the route of f-150 coils you will need a good set, possibly from the junk yard and just make sure they are the same diameter as your Rangers coils, then bolt them in.
If they sit the truck up to high, make sure the coils are seated properly, and if they are, and it is still to high, you can cut a coil out of them until satisfied.
Oh you might want to make sure you get coils out of a I beam F-150.