I guess you don't want any female responses to your question?

 

Google search: "G35 Rear Differential Bushing" "Differential Subframe Bushing Collars"

Those will stiffen up your driveline for racing nicely. There's always more to break but that's a good place to start. A well maintained stock G can drift fine but at the age of most of these cars they really benefit from upgraded bushings and rebuilt suspension components if you're going to be beating on them.

 

Buy the whole rear energy kit and a whole energy subframe bushing kit. It's a worthy upgrade with a lot more diff noise.