The d/w trucks are notorious for fuel mileage or lack thereof. My old 78 w200 being all time 4x4 and a 360 with 4.56 gears, might get 5 mpg. Wanting to take it on power tour one day so I’m considering dropping the gears from 4.56 to the taller, 3.55s, will that really help enough to get closer to 10 mpg?