Rip Rook and Piers had the best price when I was looking (they were the same $$), but the only people who had any in stock at the time was Jegs.
Just swap them out one for one using the torque pattern for the head listed in the repair manual. I would use that same pattern for incremental re-torques until you reach your final torque value. No need for a new gasket, or to remove the head for that matter. Someone had posted some really good step-by-step instructions at one time. Maybe someone can find that for ya and post a link.
67 lbs of boost is the most I have seen on my truck.