1973 Chevrolet Vega stalling

I have a 1973 Chevrolet Vega which has a problem stalling if I drive above 45 for a little while and occasionally if I accelerate from a stop. I have replace carb, fuel pump, fuel filter installed an electronic ignition and crane performance coil. I thought it might be oil pressure switch but I bypassed it and still had the problem. Any help would be appreciated.
Thanks, Bob