Figuring spring selection might be more critical on something that may be raced. I have no real experience making selections for race applications, see Santhuff, Moroso mentioned ... other than a brand name what is it I should be looking for? Why not buy from Ames? I would like to help them do well as they are a Pontiac business and close to me, if I can get what I need from them. They dont do H-body though and looks like my screamer will end up being one. Potentially 600HP tubbed H-body with Ford 9 and frame connectors.
Guess I can think of coil springs like a valve spring, tho I havent seen these specs mentioned ...
Spring material, metal treatments, coil spacing and wind shape
Would guess stiffer than stock springs in front and less in rear to aid weight transfer for traction for strip .. these probably wouldnt help handling on a curvy road in street application. Would prefer not to have to modify ride height, never liked the "jacked up in back" look or stickers and decals look. Maybe just quality coil springs correct for application with air bags to modify spring rate as necessary. Similar with leaf just add Calvert traction bars. ?? Dont know how to "sift" the choices just speculating. Need to make good decisions the first time without breaking the bank as my resources are limited.