RC10gt rtr shocks
 

how do I make them so I wont bottom out in the back? they come with weak springs, and I dont have money to replace them, Also, what would be a good replacement shock?

You can't really fault the associated shocks, they're not the easiest to fill, but the quality is top notch.

Fuel tubing should be your answer - a short length on the shafts will form a flexible bump-stop, which should stop your bottoming out.

Experiment with the lengths to get the result, but make them equal otherwise your car will start to handle unevenly.