I'm replacing the brake booster on my Ralliart with an Evo x one, but the studs are a different size, so the old nuts don't seem to fit. The Ralliart ones were M8, but they're a little too loose on the new booster. I'm guessing M7? I'm working on the car out of town, so I figured I'd ask before I waste 2 hours on the road.

It's a used booster, so is it possible that the previous owner swapped out the studs? Seems unlikely but I find it weird that the studs would be a different size.