An adaptable rack chassis for accommodating electronic component sleds of differing widths and heights is disclosed. One example chassis includes side walls and a back wall with registration features at different heights. Shelves may be attached to the registration features at different heights. The front end of the side walls may be attached to shelves at different heights. Another example chassis may have an adaptable horizontal bus bar structure that is located to the back of two side walls. Another example chassis may have vertical bus bar structure that may be adjusted over the width between side walls.