I have searched the CRG website but could find no info on steering boxes and what the numbers on them mean. I have a 1969 Z/28 RS with factory power steering. I am trying to determine if the steering box is the original one or not. The numbers I could find on it are as follows: 56865 then either a 3 or a 5 followed by a 5, 913 4, and 339 8. Any help with what any of these numbers mean or designate would be appreciated. Thank you.