In the carb rebuild, you need to inspect the tops of each primary venturi to see if each of the small holes at the top of "tubes" are open and the passages under them are alco completely open. Those are calibration points for each of the carb circuits. The one which matches the solid brass tube underneath is for the idle circuit. The other one is for the main circuit. IF you block or partially decrease the size of those holes, it richens the calibration, no matter the main jet size. IF the bottom of the brass idle tube is blocked or restricted, it will lean that circuit due to a decrease in fuel flow.
On the top side, putting a small diameter solid wire into the idle bleed hole, it would make that one venturi circuit rich enough that fuel would literally drip from that one venturi.
As to the base gasket, I would recommend the thicker one with the plastic bushings in the stud holes. This way, it is a temp insulator and the bushings keep users from tightening the hold down nuts such that the baseplate might get cracked from uneven torques. Without those bushings, it can be easy to crack a baseplate. Ask me how I know.
The additional thickness might make the choke calibration a slight bit leaner, so a slight lengthening of the basic choke rod might be needed, but not very much at all.
While you have things apart, you might also verify the carb has the correct jets and they are tight.
Now, what carb is on the car?
CBODY67
