I've been down a similar road with my '87. The only other rather simple thing that I can suggest that you didn't mention but probably already checked is the plugs, wires, and cap and rotor. My own experience suggests that these may be a major part of your problem.
Other areas to consider would be the fuel distributor and its associated controls. Unfortunately (for you), I've had no problems with these and therefore can't offer any advice. There is a lot of information in the archieves on these subjects however.
PS If I've done my math right, this should be my 100th post and should make me a Senior Member