The G8 GXP was without question the best Pontiac built in recent times before the brand's untimely death. Fortunately, that car is alive and well but goes by the new name of Chevrolet SS. But there are still plenty of old G8s still on the road, such as this particular 2009 G8 GXP. Its original owner has kept it in excellent condition and there's only around 25,500 miles on the clock. However, the owner did make one significant modification along the way: he swapped out its stock LS3 6.2-liter V8 for the Corvette Z06's 7.0-liter LS7.

The car was further enhanced with ported and polished heads, forged crankshaft, a custom camshaft, and front and rear Brembo brakes. Along with some suspension work, various exterior upgrades and even a GM Motorsport short shifter, this puppy is now up for sale with an asking price of $49,900. Not convinced it's worth the price tag? This thing did 487 horsepower and 463 lb-ft of torque on the dyno. The standard G8 GXP was good for 415 ponies. So until Chevy opts to drop in the LS7 into its the SS sedan, this modified G8 GXP could very well be the best four-door GM performance machine out there.