Y'know, I'm not sure, I'll have to look and see what kind of nuts are on there. As for the hubs, recently I tried to take a 15" wheel with a 5 bolt pattern and 114.3 spacing and put it on a car that had 16" wheels and it wouldn't fit. The 15" wheel had a slightly smaller diameter center and wouldn't go on the hub that had the 16" wheels. The 16" wheel went on the car with the 15" wheels no problem though. The lugs were the same threads, the bolt pattern matched up fine and the car drove fine. One was a Dodge Stealth/Mitsubishi 3000 GT and the other one was a Chrysler Concorde.
I see no reason why a wheel from a Ford with a 114.3mm spacing and 5 lugs can't go on a GM or a Toyota with 114.3mm spacing and 5 lugs. As long as the offset is similar, within a few millimeters.
As far as the difference between 114.3 and 115, is .7mm enough to not allow a wheel to fit? I'm probably going to have to just try it to really find out unless someone here has actually already done it and can say for sure one way or the other.