I remember when those were for sale originally, wasn't impressed then and not now either. Just a style trim option group, Cascade stood for the Cascade Mountains, so yes it was an OR/WA regional option. Wentworth Chevrolet-I went to school with Ann Wentworth, the daughter of the dealer who sold that car.
No, not different. Special.
Seriously, your car looks cool and that's an original and uncommon color. I think you're going to get a lot of compliments, especially here on this site, once she's finished up.