Assuming that the bad head gasket has not left coolant sitting in the cylinders, the things I would do are as follows. (I'm sure there's a lot I'm going to miss here) I would inspect the tires for cracks, broken belts, and tread wear. Inspect the wheel bearings and seals if its been sitting for a few years. If they looked good, I'd clean them up and pack with new grease. Clean up the brake calipers with a wire brush and check the seals around the pistons. Inspect the clips, sliders and pads. Inspect the flexible brake lines that join the rigid lines to the calipers for cracks. Pull the rear drums and clean all the crap out of the rear brakes. Make sure the adjusters are working properly. Inspect the wheel cylinders (I'd probably just replace them as its easy and they don't cost much). Inspect the drums and shoes to make sure there is plenty of meat left. Inspect the parking brake cables and adjust as necessary. All the brake lines and fuel lines that hug the frame need to be looked at for any really rusty spots. The last thing I'd want is to blow a brake line on the freeway. Change the brake fluid. All the steering components should be checked over and greased. Pretty much anything that could cause an accident if it were to fail would be my first priority. Second priority would be things that could leave me stranded like bad coolant hoses and worn out belts etc. I'd replace them all when doing the head gasket. Replace the thermostat. Drain the fuel and pressure test the gas tank. If the gas in it smells really old I'd keep it for starting campfires and start with fresh gas. Change the fuel filter. I'd pull the caps off the battery and check the electrolyte level, topping up if required then charge it and take it for a load test. If the truck has been sitting for a few years with the battery in it, the battery could have frozen and may be bad. Change the power steering fluid. Change the differential oil. Inspect the hanger bearing and grease the universal joints. Lastly I would install a new set of wipers because wipers just don't last as long as its been sitting. That would keep me busy for a few weeks.