This uses the new mudguards Lego introduced late 2016. 2 orange ones and 2 black ones are in the Stunt Truck - 60146. As of last week Bricklink did not have any for sale but the part is listed. The main body is 6 wide SUV using the larger tires and of course with the mudguards it is almost 8 wide. ADDED: Firas was so nice to me, he edited my photo and sent it to me! Hey Firas my brother, thank you so very much!
Quoting Florida Shoooter
Well done! The new fenders work really well on your model. The 'bling' def adds to it as well. We ran into a guy at the store that bought 6 of those stunt truck sets just to get those fenders. :)
Hey Florida, thank you very much. The mudguards are listed on BrickLink but no one is selling any yet. Not sure of a price yet myself if I was to do it.