What brushed motor is in the Sandstorm now? I safe bet would be to go with a HobbyWing Qicrun or EZRun ESC motor combo. And then you have SkyRC Cheetah/Toro ESCs, Castle Creations SCT Sidewinder ESC motor combos, Speed Passion, and many others. Just try to look at the reviews before making a purchase. Generally the "name brand" stuff is reliable. I don't know what price range you are looking at. Running a 2S or 7cell battery pack and a moderate powered motor...60A ESC would suffice.