What engine did you have/do you have now? The servo (the vacuum diaphragm) is different depending on what engine. Aside from that the only other parts are the two speedo cables, the transducer (mounts on the fender), the vacuum lines, an electronic brake pedal switch (to cancel cruise), a vacuum dump switch on the pedal as well, and the turn signal stalk with the button.
I could be wrong but I think 81 was the first year for resume type cruise which added a couple things to the transducer and had a different turn signal stalk. Not sure if that was the only cruise option or if you could do either one.