You may have a problem with the stall converter , if it is stock with a long duration cam . often you need a 2200 rpm stall or higher .
You may also need to add small holes in the primary throttle plates to allow the throttle to close but still allow more air in , start with approx 3/32 drill bit .
Also restricting the idle bleed orifice is often helpful , not sure what carb you have though , on a Holley type carb if you look into the carb throat you will see 4 small brass insert on the front wall of the primaries & rear wall of the secondaries , try inserting a small diameter wire into the holes & see if ti idles better , you can leave the wire in place , I recommend bending the wire into a [ shape , inserting it into both bleeds & trapping it behind the squirter
