Should be a tag on rear axle. You can also look inside of glove compartment for sticker with info. Still cannot find it call Ford dealer parts and give them your vin#.
Also if your factory tires (shown on the door sticker) were P255/70-16's then it should have 4.10 gears. If they were P235/75-15's or P235/70-16's then it should have 3.73's. But the axle tag is the only way to know for sure.
Yeah, I'm an idiot. Someone mentioned tires, and someone mentioned looking at the sticker on the door jam, so I'm looking at the Tire & Load specs on the jam itself, rather than the sticker on the door.