The engine shouldn't be shaking. Not even at lower idle speeds. That usually indicates an imbalance. One carb is doing more than the other be that air, fuel, or adjustments.
Basic idle is 850 for non a/c. But that can be anywhere up to 1000 due to your engine's state of tune.
It helps to know what version of carb(s) you have, so a picture will help unless you know you have idle screws or jets on top. Not just butterfly screws.
So do this:
First make sure there's no fuel dripping down the carb. Visually. Also you can hear it- sounds like bacon frying. It means there's something wrong with the float or the butterfly adjustment is way off.
There is a small hole on top, next to the brass air jets. Close it off- speeds up, slows down, or smooths out. Do the other. Chances are greater that one carb is off; usually not both.
Let's assume you have the carb version with the seperate idle screws. The car will actually run if you turn them in and close off the second idle passage. maybe 600 rpm. Or you can equalize those to screws to say a turn and a half to 2 out from closed.
Next, you have to magically balance the air on both carbs. Listening is one way... rubber hose, stethescope, etc. The sound of the his and the exhaust note. Or buy an air meter.
Once that's done then the fine tuning starts by using the aforementioned idle screws. Rarely will they both be the same turns. Slow steady and methodically.
Go back to the little holes on top and guage if both carbs have the same effect.
Sounds simple.
