Really, i should of not gave you that answer. I was just thinking of a good spring recommendation for a nice 390/420 average build. To give an accurate suggestion it depends on rpm, cam and valvetrain weight used. The 966 is a bit more harder on valvetrain and cost a litttle power if your not planning on running over .500 lift at the valve and trying to turn engine 8k+. With stainless 1.5" intake, .475 lift @ valve, roller rockers, and lightweight moly pushrods 7500 rpm is not a problem with a properly setup 965. Comp uses the Pacaloy material on their 965 and doesn't on the 966 and that is really why the 965 was my first answer in reference to to your question asking about "really good ones", i was thinking quality.