Are you referring to these, because they are far from $13.00 bucks! Yikes! 32 bucks??
1974 Plymouth Duster Parts | MN2300 | 1970-74 Mopar A-Body Fuel Line Clips 3/8 9 Pieces | Classic Industries
Do you have a link to the ones that you're referring to?
Maybe they are different on a '68 Coronet? I don't know what your clips look like. I believe mine are similar to the ones in the link I posed above from Classic Industries.
