carb question

[mike price]

I have a 1970 barracuda gran coupe with 383, p/s, p/b, automatic and a/c.

Idles at 1200 - 1300 rpm when air on and in drive.

turn off a/c and idle goes to 1500 rpm.

Carter AVS 4734s carb on board.   Book shows it should be a 4732s.   Is there a difference between them ?  That is making this happen?

If i try to turn down idle, car dies out when a/c on and in gear.

Thanks Mike

[Bullitt-]

Vacuum leak or could be Idle transition slots are exposed... solution is to back off the idle screw which may or may not require more advanced timing

about half way down in this article 
http://www.superchevy.com/how-to/45638/

Item #2 is a transition slot

[Chryco Psycho]

 
Advancing the timing should help it run better , it would be worth checking the float level too , I usually set @ 3/8" not 7/16