I second Br3w City comments with the following caveats:
measure the travel of your suspension, and try and put the shock in so it has just a bit more travel when fully aired out, I know lots of guys who laid the truck out on a cruise and bent a shock or broke a mount because they hit a bump. A good auto parts store will let you measure a bunch of shocks.
get a gas charged shock, airbags have more oscillation than a metal spring and a standard shock will be foamed and useless in a very short time. Monroe makes a great rear shock, monroe MON31000 shocks for $30 a pair. They are 12" compressed and 19.5" extended, about 8" of travel, part number is 94008. They would work up front too if that meets your length between shock mounts when laid out.
http://www.amazon.com/Monroe-31000-Monro-Matic-Sho...