If you're making enough power to snap the rear axles, about the only option on upgrade units are the chrome-moly axles that Rotary Performance offers.  There are not cheap!  The stock rear axles should be able to handle 400 lbs/ft of torque, but some wide drag racing slicks could cause enough load to snap them at lower torque levels.

Rotary Performance

Questions?  Comments?  Send mail to:  reted@fc3spro.com