Hi Paul, my name is Hal
Have you checked to make sure the fast Idle cam is off and the choke is fully open?
That is what i'm referring to. The front butter flys are the small discs attached to the shaft.
There is a screw on the drivers side of the carb that is for the base idle adjustment.
Turn it out so the shaft will close the primary butterflys. This will lower the idle.
Look at the picture below . do you have a idle control motor that looks like #82 in the picture. If so , we may need to make sure it is operating and if it is , we will need to adjust it.
Note this is the factory carb, is this the style you installed?
It is located on the drivers side and it is pretty large , you would not miss it. It touches the throttle lever where the cable attach's.
Base idle should be about 600 rpm in gear( D) If it has the idle control motor Base idle will be 475-500 with the motor shaft not touching the throttle lever.
I will walk you through the adjustment if you need help.