I have an '09 car so for what it is worth, the main difference between '07-'08 is I didn't have to deal with the clutch TSB problems as mine was built after August 2008 when they corrected the problem. With that said, my purchase was more nostalgic to my childhood dream of owning a 1966 GT350 and the throwback design of the original GT500. 10+ years later, I still get a kick out of driving mine. However, I had to do a TON of upgrades to get the car to handle, stop, and accelerate properly. You will want to find a low mileage car with the proper mods already completed and it will be worth the money to pay a little extra. The stock 2007 - 2009 GT500 is a wobbly pig.
Here is the list of upgrades I did to my car:
2009 Shelby GT500: 524.8 HP/549.9 Ft. Lb. Torque at the wheels on SuperFlow AutoDyn 880E AWD Chassis Dyno – Estimated HP at crank to be 619 HP
True Forged Chicane Wheels w/ Michelin Pilot Super Sport Tires: 275/30/20 Front and 285/30/20 Rear - Shelby/Wilwood Front and Rear Racing Brakes - Shelby GT500 Brake Duct Bezels/Front Brake Duct Kit - Ford Racing Ceramic Coated Shorty Headers - Shelby Oil Separator - Shelby GT500 Engine Coil Covers - Metco 2.6 pulley/idler w/JLT Cold Air Kit and SCT Tune - Shelby Billet Aluminum Racing Oil Pan - Shelby Extreme Duty Heat Exchanger - McLeod RXT Performance Twin Disc Clutch - PST Carbon Fiber Drive Shaft - Ford Racing Low Profile Differential Cover w/ over flow tank - Flowmaster Exhaust - Shelby Racing Front and Rear Sway Bars - Shelby Bumpsteer Tie Rod Adjuster - Shelby Sway Bar End Links - Shelby K-Member, Radiator Support, Chassis Support, A-Arms, A Arm Support Brace - Shelby Billet Aluminum Watts Link - Metco Billet Aluminum Rear Lower Control Arms - 2014 GT500 Upper Control Arm - Ford Racing Springs - Shelby Six Speed Shifter Lever w/ Shelby GT500 Shift Knob - Shelby GT500 Engine Billet Aluminum Cap Set - Shelby Hood Lift Kit - Shelby Billet Aluminum Racing Pedal and Dead Pedal Covers - Carbon fiber upgrades: Front Splitter, Rocker Panels, Rear Mud Guards, Rear Diffuser, Side View Mirror Inserts, Hood Vents, Door Sills, Speaker Rings, Center Console, Mirror Switch Covers, Door Lock Bezels, Radiator
Now the car is one of the best handling GT500's you will find and I feel is a proper sports car. Good luck with your search.