American Motors: 1966 Marlin, fuel pressure gauge, electric fuel pump

Question
I bought the car and they had had the fuel tank boiled out and coated new fuel lines put on...car started and ran good till put under a load it would die and would be hard to start or have to be towed home. I had the Carb rebuilt and still had the same problem.I thought it might not be getting the fuel prusure to the carb so I put a Holley red electric fuel pump on and it still having the same problem about dieing but it starts back but will die again the tow company knows me by my first name I love the car please HELP me

Answer
Hook up a fuel pressure gauge at the carburetor and measure the fuel pressure.
Have you replaced the fuel filter? Does it idle OK? If you drive gently, does it work OK?
When the carburetor was rebuilt, are you sure ALL adjustments were correctly made? i.e float level, new power valve, etc.
Does it hesitate when you go to wide open throttle when sitting still in Park? Is the proper power valve installed?