They sit slightly undersized (at least for my 1970 caprice) but that’s perfect because as you tighten it down the aluminum frame conforms to your existing hub created one of the best fits I’ve ever seen on rim spacers before.
Remember to tighten in a star pattern and be ready to sweat, had to use a 36 inch breaker bar while tightening to get it to pull all the way in but we’ll worth it.