I've tried 4 different carburetors on my 383. a 600, 670, 750 Edelbrock and now the 750 cfm Holley vacuum secondary which is by far the best one. One I've not tried is the 770 Avenger. Another one that seems interesting is the Summit Racing brand 750 carb with annular boasters which are superior on the street. But I also notice that some race carburetors have annular boasters, too. Most carbs have straight leg or down leg boasters.