I have two sets of Comp 918's that I am no longer going to use, I changed course mid build and went with a milder cam(Lunati version of the LPE 211/219) and the Comp 915 spring.
The "new" 918's, in their original box, are modified to fit the stock steel LT1 valve spring locator.
Check out the pictures.
You might notice that the stock 915 spring(darker color), same dimesions as the 918(lighter color), does not sit flat on the steel locator, it sits "up" where the coil winding ends and has been sanded flat, ie., it is wider and sharper on the inner edge.
I took a small sandpaper flapper wheel mounted in a air powered die grinder and carefully radiused the 918 spring bottom untill it would sit perfectly flat on the stock LT1 steel valve spring locator.
The set of used 918's are unmodified and I do not know the mileage on them, sitting side by side withthe new 918's I could see no obvious difference,, ie., no sag etc.
The "new" 918 for $100 shipped in the USA/Can.
The used 918's for $80 shipped in the USA/Can.

Pictures:

http://www.ls1tech.com/forums/parts-...l#post14597930