stock slant super six muffler?

I looked it up and the 79 Volare used a 17" long shell/body and the entire muffler was 22" long. Any of the A-Body 18" body mufflers would fit and work well. Goerlich has 18" body mufflers as does Magnaflow. Yours is offset center and it looks like they were 1.875" in and out and maybe the Super six was bigger? Not sure about that.
Tom