17" versus 14" tires

2005 mustang GT stock tire size was 235/55R17, assuming it stayed that way through the end of that generation (2014)

Ah, could be. I was thinking late '90s. I know the year wheels I have used a 245/45R17.

Be aware that a 235/55R17 is about 27.2" OD, while my 245/45R17 is 25.7" OD. That's a pretty significant difference in height. I know my tires get close to the middle bolt at the rear of the front wheel opening, can't imagine there being more than 3/4" of clearance on my setup. But maybe it will fit depending on offset and tire alignment. My gut says no, almost certainly if you have less offset than I do (+30mm - 1/4"?), but I haven't tried it.