I stopped worrying about mileage 40 years ago. You can't do a whole lot about it. If you start spending money "improving" gas mileage, with this and that part, you will never get that money back. There are many things in life to be concerned about. Mileage is not one of them on an old truck. Drive it the same speed every one else is driving and when it gets low on fuel, put some in. How much was the 3:55 rear end? How much was the GPS? How much is the adapter? What mileage are you getting/Were getting with the 4:11? How many miles do you drive per year? What is the price of gas in Canada? You don't usually buy an old truck to gain fuel economy over your other vehicles.

Right is right, even if everyone is against it, and wrong is wrong, even if everyone is for it. - William Penn