I pulled this off the internet.
Note where rim width and backspace are to two different points. From the rims I have seen and measured, the difference between measuring inner wheel lip to outer wheel lip and the rim width dimension is usually around an inch.
Recheck the dimensions for backspace and forward space - not shown but would be from the mounting flange to the front lip. So place a straightedge, a ruler or a level across the rim lip (not the tire face as you do have some tire bulge).
From the dimension you gave, you would have a 36-40mm offset. What model Mustang are they designed for because that is S197 or S550 offset numbers.
As I said above, take out the 10mm spacer and your rubbing may just go away - or do you start hitting something on the inner side (control arm, shock)?