I found out years ago they by installing and being able to say I had REAL Super Stock springs on my car, I picked up at least 25 rear wheel horsepower. This was backed up by both track and dyno testing at 5000 foot plus altitude.

1970 Duster
Edelbrock headed 408
5.984@112.52
422 Indy headed small block
5.982@112.56 mph
9.42@138.27

Livin and lovin life one day at a time