I would make another call. That hard to believe. I bought mine years ago for my 71. There’s are correct for a Monte. Chevelle will work but needs to be stretched at the roof quarters. Remember that at the rear above the trunk the seams need to be adjusted to line up with the trunk opening. Just order a extra piece of vinyl and have your installer make the correction. Chevelle’s are wrong. Call Legendary again and ask again. Maybe a different sales person.