Hardy,
Just did a search on OBD1 and it looks like GM started this protocol in '82. I am not familiar with your system..if it has an O2 sensor in front of the cat. The dual exhaust would probably result in minor power differences, but, with the proper muffler, could make the rig sound nicer. The muffler shop would be knowledgeable on the smog requirements...you don't want any hassles at inspection time!
Stuart
