It would really help to supply some info. What are the components that the belt would travel on without the a/c compressor involved? Is there a spring loaded tensioner involved? How many ribs is the belt that would be replaced? Pic of it would help too. We are talking about a 30 year old vehicle and that is not something that any member can just walk out and pop the hood to see what is needed. Is there an air pump involved? C'mon man!
Most of the time there has been a substitute belt found for that but in order to know for sure, some of these questions need answered. Typically, if there is a tensioner involved, just use some string and route it around all components concerned and then subtract about 1" in length, maybe 1.25". and get that length and start from there. May want to get a belt a little longer and a little shorter and take back what is not used.