Nothing wrong with a 4ac, if the one in the mrs car didn't let go then I would still have one in there, best upgrade is a set of extractors (can be quite costly for them and rare, only set I have seen IRL was a set I had), another carby if you think it is necessary as the one on them is fairly good and give it a good service - plugs, fuel filter, air filter, oil and filter.
Also check out the ignition leads, cap and rotor to make sure they look good, another thing to look at (if you have the standard air filter) is to see if the cold air intake switch is working, when the engine is cold vacuum is applied to the cold air intake valve on the filter intake, the air filter then takes warm air from the hot box on the exhaust to aid in cold starts, when it (the engine) warms up the switch 'should' close up and allow the valve to bring in cool air.
Get the engine up to temp and pull the vacuum hose off and see if it is sucking, if it is then the switch is buggered.
Let me know if you are unsure what I am talking about and I will post up a pic.