need some advice, running 3/8" fuel line, how to run, what to use

classic industries has a set of clips for 3/8" fro $13

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?

I went from 5/16 to 3/8 on my 68 coronet, used the factory clips with no problem ...

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.