Apart from the chassis kit, Servo City has a whole slough of parts for your next robotics project. The suspension system on Nomad was adapted from the Mantis kit. Extra rails, spring, brackets, etc. are all from Servo City. And don't forget the screws, lock washers, nuts, and everything else.
The Nomad project got its name from the chassis kit I originally reviewed for the March 2015 issue of Servo Magazine. The chassis is part of the Actobotics line of robotics parts from Servo City.
This is the Github repository for the project. Here you'll find the files and code for the project including all of the ROS and control code as well as any of the design files.