I have to reply to this....
You can not learn about american muscle cars from the GT series. Sorry, you are going to miss out. I have owned a few myself over the years. PD has got them wrong, plain as that. Some of the exaust sounds are pretty good, and they did get some of the "numbers" right, but all in all they got it wrong. Here is why...
First, as much as a simulator as GT is, it can not hope to capture the feeling of raw untamed power those old cars had. I am sure the physics engine does it's best to represent the cars ability on a certain track, but people didnt buy those cars for tracks. they bought them because in america, especially back then, the road was open. Pretty much any small town USA you could find that stretch of road to go "open her up". Tight corners, lateral g's...what? Who cares? 90% of where this car is going to go romping around is highyways at speeds between 50 and 150 mph depending on what you bought and where you are. The cars really can not be fairly "evaluated" in a race track simulator.
Another thing... despite being numerically accurate supposedly, none of the many old muscle cars I have driven or taken rides in perform the way the standards in this game do. They dont go 40-50 mph in first gear, and top out at 125 mph. I really think a lot of the character of those cars is lost in the total lack of choice for what were factory options back then. For instance, a 1969 mustang had a choice for engines: 2 straight 6 engines, a 289, a 302, (2) 351's, a 390, a 428 and a 429. I forget but the 427 may have also been offered. There were at least 2 different automatic transmissions offered that I know of off hand, and pretty sure a 3 speed stick and 2 4 speeds, but I would have to go look it all up again. That doesnt count the different gear ratios found in 2 different rear axles. And the real kicker is, over the years (unless it is restored for a collection) most of these cars get parts swapped. Some of the factory options were....less then dependable, while others were totally bullet proof. So people swapped them around, for durability, and performance. I had a 70 mustang a few years ago that had a 351c from a 71, and a top loader 4 speed from a 67 Ford full size car.
Which brings me to the last thing.... These cars are not hard or expensive to update. Disc brake conversions arent very expensive and have a huge impact on brake distance. Suspension upgrades and rack and pinion steering arent that uncommon and the cost isnt really out of line compared to replacing worn items with factory parts. Dropping a T5 or TKO 500 5 speed into a classic muscle car is fairly simple, complete kits are readily available including the transmission for between 2k-4k depending on how stout a drivetrain you are after, and guess what? It doesnt come with a monstrous annoying whine that drowns out the engine! This is something that apprently is totally lost on KAz and crew. Part of the fun of american muscle is modifying it. Older cars can be found for cheap and upgraded for cheap. Mustangs and Cameros/trans am from the 90's can be bought and upgraded to performance well beyond the new ones for 25% of the cost of that new 2011. But thats a different thread.
Really, the bottom line is you can't experiance a muscle car with GT. PD made a good efort at representing them, but they just dont have it right, and you cant convey the feeling of that heavy beast lurching and the front end lifting slightly from sheer ft/lb's after every shift. Watch the car chase scene from Bullet with steve mcqueen. Raw. And those are two of many makes/models that possesed that raw power.