1968 340 AVS 4425S carb problems

The area where the needle contacts the carb main body is weak and can crack. Look closely. I never could get the original AVS to run as smooth as a Holley 750 on the 383 in my 68 GTS. I drilled out the idle mixture screws which were hopelessly stuck and replaced them with the typical mixture screws to no avail. The car would run okay, however it idled rough and the tuning window was very short. Some day I will figure it out. My next step was to lead the air idle air bleeds and re-drill to richen up the idle circuit.