Well if you believe the guy i bought them from, they came "off a 600hp 351W that was in a dirt track car". I don't know about all that, but they're hogged out pretty good and have 1.94s in them. I have a buddy who has a similarly built 347 but his cam is an Ed Curtis cam, has a little more lift, he's EFI and has Victor 2.02 heads on it and he made i think 380/399 at the wheels. If 205s are worth 35hp+ at the wheels over my C9s, i'd buy a set.