My thought is that a 17" x 8" is going to be both too wide for the car, as well as too wide for the tires you would intend to install...

I put some 15 x 7 wheels on my 1800 with a near perfect offset, and it required modification on both the inside and outside of the rear fenderwell, as well as some sledgehammer work on teh backside of the front fender.

Granted, I used tall tires (205/70). And...them tires are really too narrow for my 7" wheels. I would guess that even a 225 will be too narrow for a 8" wheel.

I'll be the first to admit though that I'm certainly not the final authority on the subject... But I I were you, I'd be searching for something smaller in diameter, and narrower. You should also double check the bolt pattern... I don't know if the new Mustangs are the same. Wouldn't be surprised if they have changed since the old days...

The wheels I used came off a Jeep Wrangler... see pic below...

-Matt