So on this 1978 Z-18 I just picked up, I removed the aftermarket speakers believing that where the left rear speaker was they cut it out since the 1978 GM Electrical diagram only shows an option for one speaker for the rear, listing it as the right rear and it would be installed by Body Company. It's actually stamped out like my other Camaro. So would I have to believe a RPO exists for dual rear speakers in a 1978 Camaro? Unfortunately even tough this is a California built car, the seats were not the original ones, hence no build sheet. I haven't dropped the gas tank yet but after the age of the vehicle I doubt that ones is even legible, let alone still there. So if any of you'78 owners have dual speakers in the rear, please let me know. If you know the RPO code, that would be great as well. I used speaker as a search word on the RPO web site, but no year is given for any RPO that lists speaker options. Thanks.