If Tim has a part number of a spring that will work with your cam then I'd trust him. He is a sharp engine builder. There is a place in MI that builds a lot of the valve springs used by the cam companies. I forget the name at the moment but they have a big selection of beehives. My guess is that Tim is hooked up with them directly.

Google is my friend: PAC

http://www.racingsprings.com/beehivesprings.asp