Well, American Racing turned out their first set of magnesium wheels in 1956, and the first Torq-Thrusts in about 1961, so yes, the wheels were around in 1968.
In fact, they were standard equipment on 1965-66 Shelby GT350R Mustangs.
Unfortunately, too often, I have to remind people that 1967 GT500's looked like this.....
not this aberration and the multitude of fiberglass wearing poseurs it spawned.
Well, that's certainly true, Toronado. 14x7 Firestone wide-ovals and an iron 428CJ over the nose of a cut-up Falcon chassis do not make for a cornering demon. That's why I've always been more of a GT350 fan myself.
Of course, one of my all-time favorite comics stars a 1967 GT500, and the gun-loving bounty huntress who loves it.
It's nice (in a rice sorta way), but there's too many problems for it to be "cool". Aforementioned ride from Frank Bullitt aside, and the TVR/Vantage/250GTO/other-real-muscle-car brigade, one only needs to look to the movie industry for a short list of cool cars:
They only thing that makes a Trans-am/Firebird, Delorean or Torino even remotely cool is their association with being in a film - not vice versa. A Mustang fastback was cool even before Steve McQueen got in one. The same with the DB5 and Bond.
You could argue that it depends more on who drives the car in a film than the car itself.
Steve McQueen & Sean Connery = COOL
Burt Reynolds, Michael J Fox, Paul Michael Glaser/Ben Stiller & The Hoff = UNCOOL
Heh, Jim, believe it or not, the manga got it right and the Shelby (as well as every other car to appear in its Chicago setting) were left hand drive. However, Dark Horse Comics brought Gunsmith Cats (the manga) over in the early 90's before the right-to-left trade paperback became standard, so they flipped the images while in translation, creating the RHD Shelby.
I must be out of my mind then, because I really like just about everything in this car. It looks like it was ready to swallow the road... A beast. 
