I think "B 7" would be non-style trim Z28 with blue interior. "B 1" would be style trim with blue interior which could be a standard car or an SS 350. If the car does not have factory style trim, it would probably be "B 7". Hope that makes sense. I'm sure others will concur or offer their opinions. Many knowledgeable folks on this site, so it will be interesting to see what replies come in.