The GTO Sport Coupe remained in the lineup for ’66. It shared the same “flying buttress” roofline as the hardtop and featured chrome-trimmed doorframes. A total of 10,363 were built, making it rarer than the convertible. This promo shot from Pontiac’s ’66 Performance Catalog shows one such GTO Sport Coupe with 8-lug wheels. Though 8-lug wheels were planned as a mid-year introduction, those plans were dropped. They differed from the full-sized versions in that they were cast-iron, and used three fins between the lug nuts rather than two.