Real ones are RPO W40..
Here's the jazz on them..
http://tlentz.oldsgmail.com/specifications.html
If you buy one or are close to pulling the trigger, don't forget GM Canada Vintage Services now documents most all '77 and newer model year vehicles regardless of where built or shipped new...YES US cars too!.
Ask for George, he's a great guy!.
http://www.vintagevehicleservices.com/options.html
Good luck!.
~ Pete