Not sure of the setup of the 89 but perhaps, if it has a carb then spacer, opening up the opening for intake manifold? Msd ignition coil or something along those lines. Better spark plugs and wire. Perhaps a performance distributor cap and rotor. New fuel filter helps. Different blower motor for the heater (pretty toasty mod)
The E fan will help free up a few ponies. If you can do synthetic oil, that helps things move a lot better.
If carberated, is it possible to swap in fuel injected intake manifold and throttle body and add in the electrical components???