That's a dumb rule. The factory cowl hood is heavy, anybody running it is subjecting themselves to a weight penalty anyhow.
Someone needs to produce a build sheet of a special order 255 HP 69 with a cowl hood and stuff that in their face.
It appears that it wasn't available as stated
http://www.camaros.org/forum/index.php?topic=10210.0
BUT, no one knows 100% for sure that a 255 HP model NEVER came off the line with a cowl hood.