Free? No. Fee-based? Yes.
FoMoCo = Kevin Marti Report
http://www.martiauto.com/reports2.cfm
Mopar = Galen Govier
http://galengovier.com/decoding.htm
Canadian-GM-produced and/or sold =
http://www.gm.ca/gm/english/shopping/parts/vintage
Pontiac Motor Division =
http://www.phs-online.com/
Your friendly local GM Dealer, through GMVIS, can source a lot of info back to certain Model Years for
ALL GM vehicles by VIN.