i got a 89 c1500 with a 350 sb carbureted with mallory hei ignition and a mild cam. This truck runs like a champ for a uncertain amount of time and then ramdonly it will stall. Some times it will start right back up some times it wont start for at least an hour or two. When it stalls it stalls like i turne the ignition off. Its got new plugs, new crane cam wires, mallory coil, accel distributor. My fuel pressure regulator is reading strong and steady. I test the ignition system and its strong too. Holley Street Avenger carb is pretty new also. Could possibly be a relay or something but im not sure any in put would help