I'd for sure use some cleaner , plus I'd change the gas filter , check the air filter , check PCV
valve , also check the ignition coil and it's connections , spark plug wires and clean re-gap or replace the old wires and plugs but be sure to check the spark gap even on brand new plugs.Plus clean the battery , starter , alternator , engine block ground posts and connections with wire brushes or fine sandpaper , also check clean the grounds and any plug in sensor connections too, make sure you either clean the old ground screws and connectors or replace the connectors and ground wires you find too.The wire should be the same gage and the wire connectors or o-ring wire connectors are fairly cheap but I'd make up some shiny new grounds and run some brand new ground wires on that vehicle for sure"due to it's age".
Check the belts and all fluid levels and I bet that vehicle could use a transmission fluid and filter change but for sure if I were you I'd add 1 litre of Lucas oil treatment instead of 1 litre of oil your next oil change too.
Hope that helps and best of luck.By the way if you use some Lucas gas treatment on that engine it will help it too , then after using up a few tanks of gas change the gas filter again , change the gas filter on a yrly basis after that.
I believe this will help that vehicle a lot and be sure you check the ignition coil's housing for cracks or bulges or extreme rust or damages etc too.