89 ford f150 inline 6

Well, I believe there is a problem with the starter once the engine gets warmed up, worn starter bushings cause the starter not to work, crank slowly, should have the starter checked. The stalling issue could be just the engine needing to be gone over, cleaning the Mass Air Flow Sensor with MAF spray cleaner and cleaning the throttle body with carburetor cleaner. Check the cap and rotor, along with spark plugs. Snug up the intake, exhaust manifolds.

Those older Fords would often stall out due to lack of spark when they heat up under the hood. The problem part is the electronic spark control module. They are a silver colored ribbed metal unit, 4"x6" and 2" thick, mounted on the fender wheel. They have wire harness that plugs into them. Lots of older Fords had them and they cut out when hot. I would throw snow on mine to get home. Check things out before buying parts but this is a common problem that's hard to diagnose. It makes sense that running the A/C makes it get worse....hotter under the hood. I hope this helps.