If you can afford it then this is a low cost option that will give you more speed and runtime.
If thats out of the question then this is a lower cost option.
Keep in mind you will likely want to upgrade this eventually also, but it will give you increased runtime and maybe a bit more speed.
If you have the older model with mechanical speed control it likely has bushings as well. Upgrading to bearings will also give you more speed and runtime. Here is a low cost set.
If you do not have a few good batteries then that is another thing you should look into. Not sure what you have but dont buy anything less than 3000mah if you want to run long enough to have fun.
Many folks on here have upgraded Rustlers, including myself. So Im sure you will get lots of responses.