Truck keeps sputtering when going uphill or when too hot

First let me say we have switched the motor with a 1978 Chevrolet Camaro Z28 motor and it is stroked and turbo. We are having issues with the truck sputtering and just completely turning off, but the electricity stays on. We have replaced the fuel lines which were not good anymore. We have tweaked the idle screw and we have put a new fuel pump in it. It only sputters and goes out when it's going uphill coming off from being a uphill and when the temperature gauge gets to the first line not even the half line the first line.