On my '73 there are 3-adjustments originally ... does yours still have a functional idle stop solenoid on the right side?
That is where the final idle adjustment was originally made, mine was removed long ago so I rely on the small screw on the left for warm idle & of course the big ole fast idle screw that rides on the fast idle cam for fast idle. Left turn lowers Right turn raises RPMs
If your mixture screws are out to far (lean) you won't be able to get idle low enough. If that doesn't solve it then could be your timing.