Here are a couple links, see if this helps you any. :smile:
http://www.348-409.com/rpo1.html
another one
http://www.yearone.com/updatedsinglepages/Id_info/decoding_body_tags.htm
and some extra info that may be useful
http://www.chevyoptions.com/1966Chevy.cfm
Hope this helps you out some, I tend to google the crap outta all my projects so I can get a clue as to what they started out as.
I decoded a 70 1/2 Z/28 just after taking it to the crusher 
http://www.348-409.com/rpo1.html
another one
http://www.yearone.com/updatedsinglepages/Id_info/decoding_body_tags.htm
and some extra info that may be useful
http://www.chevyoptions.com/1966Chevy.cfm
Hope this helps you out some, I tend to google the crap outta all my projects so I can get a clue as to what they started out as.