[Dave Casey]

I have the same cam as you , 400hp 427 , for years I used a Manley nextek spring that came with a damper and I took out the inner spring. Worked great, lasted forever, never broke one and my cam is more square nosed and my car is a stick. Still have a set in my spare motor. I believe that the only advantage of a conical spring is weight at the valve. Sorry, but I do not have the manley number, you could probably figure it out in their catalog