OK first, you have this indefatigable bias toward Pontiac. Since you live in Canada, I'm starting to think you're a direct decedent of Chief Pontiac himself.
As of 1966, (IMHO), they f**ked the Corvette up royally with that butt ugly cranked roof line.
Perhaps I'm mistaken, but, (again IMHO), the "Banshee", the Camaro, and the Firebird, all grew out of the '63 to 65' Vette lineage, not the other way around.
Now, Chevy motors run faster than Pontiac motors. (Note that I didn't say better), and they were almost, but not quite, a match for Chrysler's 413 cross ram dual quad 413 cid (1963?), and no match for the 426" hemi mills.
Now as for marketing & price, (low to high) it was Chevy, Pontiac, Oldsmobile, Buick, and finally Cadillac...With each price hike denoted by more extravagant styling, and interior luxury.
For myself, I liked the Firebird's styling much better than the Camaro. In fact, I owned two of them, a '67 convertible, & a '79. (Which was an ungodly dog, with a Buick V-6 in it).
However those "Trans Am" models, were, (you gotta admit), gaudy, tacky, gauche< call it what you will. Now, I didn't say they weren't "cool", but they were "loud", from a visual standpoint. And they did find their way into a trailer park or two. So, you have A Cadillac "El Dorado" outside the luxurious suburban home, (at least in the ad pictures), and the Trans Am outside the double wide.
If I was fortunate to live in a trailer, you'd find me alone at the far end of the row shouting, "get off my propane tank". (Not having a lawn to chase the kidz off, you understand).
And if you still didn't get the Joke, "Jim Rockford", (TV private eye, played by James Garner), lived and worked out of a trailer, and drove a Firebird.
STINGRAY:
STING-BARGE (They even call these "boat tails).
My only mistake is thinking the 67 Vette looks that much different from the "64, '65, & '66
'67
'64
Now the only real difference between the '63 & '64 Vettes, was the split window. Which they got rid of, because the split was directly in the path of th rear view mirror.
Now, it makes sense that you wouldn't design a safety hazard into a concept car, doesn't it?
This is when they changed to the flat plate "cranked" rear window, 1968 (?) 1969 shown.