One of the best parts about SEMA is getting to see the manufacturers build cars they might not otherwise. Take this G8 GXP Street Concept, for example. Sure, the 415-horsepower 6.2L V8 in the standard G8 GXP is plenty good enough, but why not stuff the new LSX454 crate engine from GM Performance Parts underneath the hood? The 7.4L V8 is good for a ZR1-matching 638 horsepower and 600 lb-ft torque, allowing this G8 to unashamedly call itself a true muscle car. Other features include stiffer springs and the brake package from the CTS-V as well as 20-inch black chrome wheels. The exterior has been given an aggressive makeover with a new front fascia with unique upper and lower grilles and a rear fascia that incorporates a diffuser and performance exhaust system. Inside are custom leather seats and a new gauge cluster. More details and plenty of photos are soon to come when we hit the show floor next week.