Those look like the pre-'73 nut and bolt factory rods that are good to 450 HP as long as the RPM doesn't hit much above 6,200 to often. For a mild naturally aspirated sbb 350, the earlier rods are around 100 grams lighter per rod than the later rods and would be able to rev faster than the later rods. That's around 800 grams of weight off of the rotating assembly, that's 28.21 ounces, that's more than 2 beers of weight! That doesn't make more power when the rods are lighter but it does free up some power when they are.
