I have a 56 Ford Fairlane with a 292 Y-Block, Holley 600 carburetor and a Fordomatic automatic transmission. I’m having trouble getting it to idle in both Park and Drive. When I set the idle properly in Park or Neutral and then I shift it to Drive or Reverse the RPM’s drop off to ½ of what they were and it'll barely run. And when I move the idle up to get the car to run in Drive or Reverse and shift to Park or Neutral the idle goes up to double what it should be. I’ve had 2 different Holley carburetors (1 was a warranty replacement) and 2 different sets of ignitions components. Local transmission expert tells me it can’t be the Fordomatic. Any ideas?