I have a 1993 Chevy K1500 4x4 with a 350 TBI engine and a 4L60E auto transmission. Truck runs and drives but is currently overheating if driven for very long. I put in a new fail safe thermostat and replaced the clutch fan. When I take out the thermostat it doesn't overheat but it never gets up to operating temperature. I have had to buy 3 or 4 Fial safes before I get a good one so I think that's whats happening. Truck CURRENTLY WON'T PASS SMOG because it has the check engine light on. It it throwing code 43 and 83. It seems to shift fine but it's still throwing that code. Odometer reads 250,XXX miles but I did an engine swap with a 350 motor with 180,XXX miles. When I did the engine swap I replaced the exhaust manifold gaskets, knock sensor, 02 sensor, transmission wiring harness and all sensors and solenoids, changed tranny fluid and filter, and brand new Magnaflo catalytic converter. I looked up code 43 and replaced the knock sensor but I've still got that code. I looked up 83 and replaced all the tranny solenoids but I still have that code. Does anybody have any insight? Do you think my ECM and/or PROM are bad? Is there any way I can test them?