If your area ( fill your profile out ) has emissions , make sure they are on there . A lot of people remove those to clean it up or to free up a couple ponies , they are likely to add up quick if you need to buy emissions stuff .
Also , like everyone else says look for body rot . It is by far cheaper to buy a clean truck with bad motor , than a good motor with a bad body .
Lots of people TRY installing stereos , CB's and gauges . Look at the wiring harness . It is much easier to add wheelin' accesories to a harness that won't catch fire or pop fuses /forums/images/graemlins/k5.gif