After a point you will start looking at ‘after-market’ goodies. You won’t find these in your local Toy or Hobby Shop. Performance parts are offered by one the four majors – Harden Creek/Viper, Wizzard, Scale Auto, or Slottech. There are also some specialty vendors. Sites like this one offer advanced cars and parts. Also look on the links pages of sites for the various specialty items.
You can purchase everything from lightweight lexan bodies that you paint on the inside, to flanged rear hubs. The better flanged hubs allow you to run a vast range of slip-on Silicone rear tires. There are independent front ends, silicone/sponge tires, lots of electrical components, more powerful armatures, stronger motor and traction magnets, – the only limit is your imagination and wallet.