If you ordered your brake parts you have to exchange them or cancel the order now. Disc brakes need different offset wheels than the original drum brake wheel. I myself would cancel that order I figure out what you need for wheels for the conversion on both front and rear axles. You may (probably) will have a problem doing the change over. I would drive the truck the way it is and not overdrive your brakes - along with not overdriving you headlights.
