When I had the axle ratio changed in my Dakota, I didn't need to do anything to correct the speedometer because the reluctor wheel for speedo pickup was in the axle on the ring gear.
Now I have a '13 Ram Sport. It was optioned with 3.55 gears and I want 3.92 gears. Do you guys know if the Rams still use the same axle? I think my Dakota had a 9.25".