Welcome to CHR, Grandpa! We're a pretty gentle group here, so hopefully you'll feel OK.

Thinking about the '67 Camaro with the in-line six I'm thinking that the distributor indent in the firewall was sized for the old point style distributor, which was about five inches diameter at the base. I'm thinking that your SBC 350 is likely running an HEI distributor, which is more like seven inches at the base of the cap? I have zero experience with Camaros of that vintage, but I'm wondering if that might be the problem? Someone else may be able to offer first hand experience to get you going.