That's my boy! Way to go! Can't help enjoying your progress on this Mack.
Bonnet is an eye-candy, but that fender is a huge trouble. Regular curved bricks is not a solution. Go in either for some unique combination of panels and tiles or simply try layers of regular plates.
Nice execution of XL-motor-tank, but watch out for scale issues. According to the pic you submitted the tank should be smaller and closer to the front wheels. Of course, it's up to you, but I love the standarts you're trying to keep up with.