[Mr70]

I only know of Two LS-6 Chevelles,(Have you seen others?),that show "450/HP painted on the rear SS Bumper pad.One Red Hardtop,one Black Convert.They were both originally owned by Bob Fuller of Iowa,and he admittedly put them there day 2 because he liked the way it looked.

That decal you show resembles one I saw in the 1980's made by a local Novelty Co.