I still have original gaskets in original Chrysler packaging from 1972,packaged in sets of thee including air horn gaskets,never opened,same as picture I posted.

As Dilbert and I previously stated, there are many things that can cause this. Need to go back over everything from square one and check everything carefully. Odds are something is binding or not hooked up properly and since we aren't there, we can't see the issue.

Turn the carbs over and look to see if the throttle blades are closed fully. If not, back out base idle screw to see if throttle plates close. Look for signs of the throttle blades rubbing in the throttle body. Push the throttle shafts side-to-side and feel for play and any binding while opening/closing the throttles.

If the throttle blades are not fully closed, you need to see what is binding (linkage, throttle plates, fast idle cam, etc.) and causing the throttle to hang open.

Then move on to check the carbs as they get installed...

Do the base gaskets show signs of rubbing anywhere? How about on the edges of the throttle bores in the intake?
It doesn't take much...

Then I would reinstall the carbs loosely and open the throttle bores to make sure they move smoothly and are centered in the bores. Tighten the mounting bolts a little at a time to specification and recheck the throttle for any binding. Repeat on the next carb. Reconnect/adjust the carb-to-carb linkage. Is the throttle return spring weak, not returning the throttle to closed position?

Reattach the throttle cable and kickdown linkage, making sure they don't hold the throttle open. Reconnect all the fuel and vacuum lines.

Check the PVC and power brake booster hoses. Maybe one got damaged during carb removal/installation. Also check to PCV valve to see if it is stuck open. Shake it, does it rattle. You're basically looking for anything that would cause a large vacuum leak. Once running, disconnect the brake booster and plug the line to see if the booster is bad.

Did you move/bump the distributor when removing/installing the carbs?

Do you still have points or has the car been updated to electronic ignition? If still points, check the dwell to ensure it has not changed. Reset as necessary. Check the mechanical advance in the distributor. Pop the cap and check to see if the mechanical advance return properly by rotating the distributor rotor and release it. The rotor should "snap back" into it's original position. Repair as needed.

Start the car.

Once warmed up:
Check the base ignition timing. Is there any vacuum going to the vacuum advance while at idle. If there is, the throttle is open too far or the hoses are connected improperly.

Turn car off.

Good luck. Keep us posted...

Yeah, dilbert is right. It's just a vacuum secondary Holley with two sets of secondaries. They do seem overwhelming to many people, but they're actually pretty simple.

Here are some pics of the setup.

Just an observation:
1- Should your choke rod be straight up instead of an angle?
2- Is your Solonoid screw all the way out and normal idle screw all the way out?
3- Normal idle screw should just be touching and then back it out 1 full turn.

Why is the gasket between the body and the base of the middle carb sticking out?

Why is the vacuum line from the T going to the choke pull off? That vacuum line is suppose to go to the center carb. I think you have them on wrong. Or is it the picture that is hiding it?

1 it is when choke is closed
2 Solenoid is not charged when it is, it rises. Screw is out so they never make contact
3 Ironically and accidentally yes it is

I see what you see. Authentic Holley gaskets installed based on how they were made and how the bolt holes lined up.

It's not. If you look closely the vacuum line from the vac advance is ribbed. The other lines are smooth. The line going to the pull off is from the underside of the center carb. The line from the T is going to the inner port on the carb same as the ports on the outer carbs. The outer port on center carb goes to the vac advance. It's just as obscured in the factory service manual. Very hard to tell which line goes where.

At this point is there a way for me to tell whether the carb base gaskets are the reason for the issue without removing them?

Did a little more research. I think the tan ones may have been for the 440 version while the darker thinner version was for the 340s.

Is there a way for me to tell whether the carb base gaskets are the reason for the issue without removing the carbs?

Had a little time this morning. Car seems to run great just can’t get idle down below 1500 or so. Pulled vac hose to advance at idle. No change. Maybe if I retard the initial timing??

From a post above,have you done this with linkage disconnected ?

1. Turn the center carb idle screw all the way out (lowest possible idle). I assume you've already done this.

Yes

That is some good technical support from the collective
I put the popcorn away for the moment.
Nice pics!
SuperPerformance base gaskets are the best
What happened:
The car ran normal before the center and rear carb came off.
Carbs get reinstalled and the idle is high.
Vacuum leaks usually mean poor idle

Start here
Be sure the distributor is not loose-see if it turns - if that's it stop and fix.
Warm up the engine to operating temp
Shut it off
Be sure the idle mixture screws are at least 1 turn out ccw
Disconnect the throttle cable
Remove the rods from the both outboard carbs - relax nothing is going to happen.
Be sure you leave ithe outboards in the closed position
Be sure to secure the rod from interfering with anything.
Be sure to actuate the outboard carb to be sure the throttle blades come to rest
Lock out the choke.
Turn idle adj screw CCW till it has no contact with the throttle blades

Check the float levels -Trickle out the ctr, just below on the outboards

Try starting the car by just turning the key [ btw a properly tuned car would start right up] If it does not run -it should not run - set the idle screw 1 turn in CW. It should start and run. Work backwards to putting everything in it's place.
No go over to the lift off hood playground where a decent version of the six pak tuning guide is and set the carbs up properly.

If it runs away like before: wiggle each outboard throttle blade while it's running.

Report back

Checked for vacuum leaks all around, carb base etc., nothing. Revisited this, readjusted, and curb idle went down to where it was before. Much better.