On a basically stock 383 with manifold heat the 650 dbl pumper will be good choice. Stick with 68-70 jets frt and no more then 76-77 rear the pump shooters are good as is in most cases unless the car is heavy. I try to tune at the track with that issue. Don't start screwing with the air bleeds unless the car is modified or you cannot get it to run right, or you got the dough to blow on th cost of the carb