My 2005 GTO has posi, and the factory donut spare is definitely shorter than the OEM tire and wheel setup. If GM sold it like that, I wouldn't sweat just driving home, or to a tire shop.
Some of the donut spares have dual fit bolt patterns so they can be used on different cars. There are also dual pattern steel wheels sold if the front and rear patterns differ.
I own 3 tow dollys, and a one ton dually, so if I can get home, I can surely get the car back home, one way, or another. I hope to finish my wrecker soon, so if I have that, I can just get to the house, and haul it home.
One time my wife had a flat on a rental car, and was only able to pull off on the left hand side of the road against a Jersey barrier, a precarious area at rush hour. It took 3 hours for the rental car company to get someone out there to change the tire, I'd hate to wait 3 hours on the interstate for help to arrive, but that's just me. I would likely have driven the car on the flat to get away from the traffic, and the barrier circumstance, just an accident waiting to happen, IMO.
I've had to drive a couple of miles on a flat when I had no spare a few times, one time was on America Racing mag wheels. Surprisingly it scuffed up the very edge of the aluminum a little bit, but the tire protected the rim much better than I would have expected. I just mounted another tire on it, and it went back on the car. Young, and dumber days....
