Absolute cheapest way? Throw a few hockey pucks where the body mounts to the frame.
You'll get what you pay for when it comes to lifting a truck. Simply adding blocks to the front would throw your suspension so far out of whack you'll be buying new tires every 5k.
Best way to lift the current configuration is to get a kit with new leafs, shocks, front axle pivot bracket and a drop pitman arm, and throw some 4" blocks under the rear.
Better yet would be to D60 swap the front and add 4" blocks to the rear. Should have you just about level.
Keep in mind the higher you get the truck off the ground, and the bigger tires you run, the shorter your ball joints/ wheel bearings/ axle u-joints / tie rods are going to last.