I'm either getting 4.56 or 4.10 this winter when i put my lift/tires on (6" 35's). Is there a price difference between the install of the two ratios? I know that the price for the gears is the same but what about the install?
Definitly 4.56's with 35's. 4.10's are standard for 33's, to bring it back to stock feel.
I recently had 4.10's put in mine at 4wheel Parts and it cost about $1900. for f/r ring & pinion, master install kit, rear axle bearings, front carrier (required for 4.10 & lower in a Dana 44) 5yr/50,000 mile full warranty. A lot of money, but what a difference from 3.55's. It is a pleasure to drive again. No loss in mileage & can't feel the tires dragging anymore.
Should be close to the same cost for either size gears.
Now as for you question about the overdrive all the time I usual use mine all the time till I get into really bad hills and upward grades. I suggest leaving it on as long as the engine isn't lugging. But if you really wish to not use it should be no problem just the rpms will be slightly high on the highway.