Phew! Thought I remembered them having a 440 car as well as a Hemi.

Nanket: the Belvedere & GTX trims being on the same car tells me that was likely an RO body with GTX trim added to be legal SS/E. Reason would be the lighter RO; S&M wouldn't have to strip seam sealer & etc.

As noted, little build details are good clues; that helped a lot to confirm history on my own car.

The name Dave Christie just popped into my head, as being affiliated with S&M, but I could be wrong. Herb McCandless may know something about the S&M '67s, though I don't know how involved he was with them at that time.