I have been working on a 1947 Plymouth Special Deluxe from my father in law that had been stored for the past 10+ years. It has a 1941 engine in it from the factory (WWII leftovers) and he had the engine rebuilt prior to storage. When he had run the vehicle all ran well with no issues. Later on, the electric fuel pump he had in it to bypass the mechanical one eventually failed and he did not have it replaced. Brakes froze up and it needed some work. I have done a complete brake replacement. also replaced coil, distributor cap, rotor plugs & wires, points and condenser, starter rebuild, electric fuel pump (pressure regulator on fuel line, new fuel filters. Vehicle starts and runs well at lower RPM but when I get about to 30 mph or so, it loses power and misses. Thought it might be timing but when adjusted still does the same. Fuel pump seems to be delivering fuel well but cant determine that when the vehicle is under load. Any thoughts on this?