The later the year, the better. I learned a few things over the years but don't quote me on any of this. I'm pretty sure that the 2007's and up have standard side air bags. Also the gearing on the early cars (2005) is shorter I believe. There's going to be little changes throughout the cars here and there like no exhaust hangers on the transmission mount on later years to stop vibration issues and also it looks like there are small wiring changes on later years as well. My 2007 V6 used to be able to keep both it's headlights and fog lights on when the key was off the ignition but for my 2008 GT the fog lights will not work if the key is not on the on position. That could be a difference between all GT's and v6's however. Also it seems like the newer cars also have their 12v socket ports on all the time while for older cars you have to have the key in the ignition for them to be on. Lastly my windshield wipers on my 2008 GT does a "final wipe" 5 seconds after the initial 3 wipes when I spray the fluid out to clean the glass. My 2007 didn't do that.... it's the little details!
2008 Windveil Blue Manual GT. BAMA 91 Performance Tune. LED Starter Button, Retro Shift Knob, SLP Loudmouth Exhaust, Ebay CAI LOL, MMD Quarter Window Louvers, Roush Rear Spoiler, Raxiom Gen5 Taillights, LED Third Brake light, MMD Hood Louvers, MRT Rear window louvers, Exedy Stage 2 Clutch, Exedy Lightweight Flywheel, SR Performance Stainless Steel Braided Clutch Line, Dot 5.1 brake fluid ftw, JLT Oil Separator, SR Performance Strut Tower Brace, SR Performance Rear Shock Tower Brace, Triton V3 Switchback turnsignals... etc etc