I like that you're forgoing the Vinyl Roof as I think it disrupts the flow of the Roof Line into the rear Quarters, Wings maybe? I think your Wheel & Tire set has the Micky Thompson Tires. They did has a wide shoulder on the treat and a 90 degree edge between the tread and the sidewall. You could try a little sanding in that area to soften the edge. The OEM colors for the '67 Impala had both a light beige color, like your photo, and a very light yellow color that was very popular here.