sweet ride! those carbs should have a main idle adjustment screw, flathead i believe that adjusts the main idle and throttle position of both carbs.. should be between the carbs.. that will lower your idle.. id personally wait til the car is up to temp before playing around with that.

least you got the belltop type su carbs.. those are much better than the flattop kind. granted theirs many intake options u can do with these engines.. my personal favorite is the su's and triple webers.

another thing thats easy and something that helps abit.. is get rid of all that emission crap on the balance tube and plug it. looks much cleaner imo.