Considering the car only had a 2 bbl. sitting on a 60 lb. iron manifold the 600 cfm is most likely a huge improvement. All the head work, totally hogged intake & exhaust. Yes mild comp L476 D270. On paper should be putting out at flex plate 1 hp. per cube. it's a 395 now. Runs great, smooth, nice lope. If I wanted big power would have dropped a 455 in her. Remember the car is for my better half, she did not need big power, heck it's all she can do to run a leaf blower !!! !!!!!