The smoking is probably from worn valve guides/seals or worn piston oil rings. So keep in mind, it may need rebuild soon. Stock motors arn't bad but it depends on what you want to do with it. With only 56 horsepower, you can't turn much, especially 38 in mud tires. But with a small engine, it comes with good fuel mileage. I have to say the stock axles are pretty strong, there are many improvments that you can do to make them stronger, although 38's may be pushing that limit. Toyota axles are expensive but worth it.