i can offer a personal testimony here. back in 1969, i had a new 68 340 4sp fastback S cuda. a friend of mine had a new 68 383 4sp super bee. we raced probably 5 times and my cuda beat the bee every time by 1 to 2 car lengths. i probably had some advantage because my cuda had fenderwell headers, a 750 double pump and 3:91 gears. all the 383 guys i knew at the time shifted at 5500 and i would shift at 6000-6500. i think the faster winding 340 will beat most big blocks all day long. i know 389 GTOs, 396 chevys, 390/428 fords were never a problem for my cuda.