EDIT: Initially, I had that bracket connected to the motor mount pin, but now it's connected to a wing on the engine block. As I recall, I did some research and determined that's the correct location. Here's a picture. It's hard to make out, but maybe it will help.
As I understand it, all but the earliest 1970 Mustangs had a built-in grommet in the negative battery cable which bolted to the fender apron. I ordered the "Heavy Duty" cables from NPD which don't have that grommet. That's why it's connected where it its.
The "concours" set I purchased had a built in attachment strap to attach it at the voltage regulator screw and it looks correct. The starter cable had nothing so I removed the strap from the old original cable and put it o the new one.