Yes the 08 Mustang Shelby GT500 is a fantastic car, but I also agree that an older rousch, cobra, or saleen mustang that is modified would be equal or higher horsepower, and would cost about half the price. You also might consider the 2009 Dodge Charger SRT-8, 2010 Chevrolet Camaro SS, 2009 Chrysler 300C SRT-8, 2009 Chevrolet Corvette Z06. If you are chasing horsepower, then get the shelby or the corvette z06. If you want speed with high reliability, get the charger or the 300c. Also, look at the cadillac STS or STS-V series, as these have great horsepower and great luxury.
If u want a true muscle car and have some mechanical know how.Why not just go out and buy a original muscle car from the 70's the horse power years and build your own Hot Rod . It may take some time and cash but the end product will be your very own creation ,Don't say know just do it and forget about these want a B cars of today.
It depends on the price of car on whether or not it's worth buying. So nobody can answer the question since that information is not present. And you cannot get the GT500 in an automatic (from the factory). If you can't drive stick you have no business driving this car.