overkill , well ran them on my 65 880 rag's 383 auto 276 or 291 r/e (?) to the tune of 6k in every gear but drive , ran fine according to the plug color with a prestolite dual point dizzy and headers . she would do 120 in second at , yes 6k . there off my weiand tunnel ram for my other 383 + .06 over bored , full race ported iron heads and tall c/r , that i went larger carbs on that . maybe over kill on a stock 383 cam . those 450's should be okay on a stocker . my next set up would have been a 450 and a 390 . more throttle responsive down in the lower rpm range , but the top end would have suffered . and i ran some ford 406 holleys , 500cfm tri carbs on a 383 6 pck intake . but the twin 660 four ran further into the rpm and higher on top speed as well . its heads and cam not cubic inches so much . and stock heads go along ways on a 383 , same casting as the 413 426 440 wedges . just valve size .