1950 Plymouth Special DeLuxe 2 door sedan. Set the point gap and timing. Vacuum advance unit works (disconnected while timing was set). Stumbles when accelerator is depressed. Suspect bad/worn accelerator pump. Did not want to take carb apart without rebuild kit in hand. Problem is that I am having difficulty finding D6H3. I can find D6H1 and D6H2 but not the 3. Is it the same as the 2 or is it unique?