8. Out comes the 305. For less than the cost of rebuilding this engine or buying an already rebuilt 305, the owner picked up a 290 horsepower 5.3 out of wrecked Trailblazer via eBay. Yes, there is the cost of the conversion parts, but in the end, this engine will last another 200k miles (with regular maintenance, provide almost twice the horsepower and better fuel economy. Because it’s all aluminum, it takes 150 lbs off the nose of the car.