How bad is the interference?  If its not that much I'd just grind off the offending points until it cleared.  I wouldn't hesitate to take 1/8" off those spots shown. 

6sally6 wrote:

I prefer to "beat-the-daylights-outta-it" with a BFH! My theory is folded metal is stronger than missing metal. Sometimes a grinder-ectomy can't be avoided though.
6sal6

 
Looks like Mike falls into the category of

Beat to fit
Paint to match
And caulk it, if it leaks!!

You MUST use a wheel spacer of about 1” thickness to install those wheels on your car. No upper control arm mods will help, only weaken the uca.  That wheel would require the same spacer to fit your car if you had the original brakes on the car. The Cobra brakes are not at issue.
The later 17x8” wheels such as yours have 5.72” backspacing. Normal maximum allowable backspacing on your car is 4.5” to 4.7”.  The 1” wheel spacer makes the wheel think it has 4.72” bacspacing instead of 5.72”.  If your car is a 65-66 Mustang, you can expect fender interference with the 8” wide wheel. A 7” wide wheel with proper backspacing woukd fit better.  On 67 and later, there is less chance of fender interference.