I have tried two quadrajets that have been rebuilt and they both burn to rich and my L48 350 will not run right, very rough idle, and just not clean running like the old one. I tried adjusting the choke idle and the two idle mixture screws and the idle but I just can't get it right, it just burns to rich, is there some other adjustment internal that need adjusting ? Any ideas, Thanks.

Did you hook up the vacuum line from the distributor to right place on the carb.Full time vacuum will advance the timing and cause it to run rich and idle poorly.