Mine's a 5 speed with 3.08s.

 

Ok so what are you getting for mileage?

 

yes it will...
you will need to go to ford with your axle ratio and the transmission tag and they can help you get the right speedo gear so your speedometer reads true. It is a very easy swap if you have access to a donor truck...

 

i get 18 hwy with 3.55's

 

Ok I got my rear end tag I'll post the picture up here when I get wifi so it will load. How off would my speedo be if I kept the original

 

Already answered that.

 

I took a picture of my rear diff tag and the photo didn't save but the number on it was H17 what ratio is that ?

 

The tag has the actual ratio on it.

 

Turns out I got a 3.08 rear end in my truck

 

My 5 speed with 3.08 rear gets 16-17 Mpg average with a best of 20 Mpg at 60-65 and 19 Mpg at 70-75 Mph. Truck has regular 235/75/15 highway treads up front and real snow tires on the rear. When hauling my 4500 lb 5th wheel RV it drops to 13 MPG at 55-60 mph not using OD.
YMMV
rikard