is the car a manual or an automatic, if its a manual go ahead and throw a double pumper on there, if its automatic use an eddy 600 or 650.... i dont have any SBCs so i dont know exactly how eddy's operate them, but i know on my 475hp 302 in my mustang, i ran a 600 first and it was too lean no matter how big i jetted it so i stepped up to a 650 and had to max the jetting to get it running best on the dyno