The guards were standard on all 67, even the Shelby. Many 68's came without the front/rear bumper guards, as part of Ford's post-strike cost cutting. Even without the Marti report, it's easy to identify non--guard 68's. The hole for attaching the upper bolt to the taillight panel is not punched.
I see a lot of cars with the wrong bolt at the bottom. The photo on the above post is correct, with the big Phillips head.
Here's a look at the exposed brackets-