87 was the first year for fuel injection (Throttle body injection), things to look for is RUST. Cab corners, rockers, around the front windshield at the bottom, floor boards, behind the rear wheels ect... overall condition of the motor, transmission? Interior in good shape? These are great trucks, just depends on what your REALISTIC expectations are. These rigs are mostly 30+ years old now, and from a generation of when people actually used them as a truck.
Here is a picture of mine completely rust free and was in pretty good shape:
