The higher the number, the lower the ratio. 4.56 gears are lower than 4.10s and will slow it down even more, unless you really want the motor to be winding out at freeway speeds. Acceleration will be great though.

For the stock gear ratio, look at the door tag for the axle code and then decode it here:

https://www.ford-trucks.com/article/...r_Decoder.html

There should also be stock tire size info on the door sticker, probably 215/70-14"