I've got 4th gen seats to go into my car. The rear one piece upper seat has a latch on both sides where the 3rd gen one piece only has it on one side. Any one know if the hole is there in the body work for a latch pin on the other side? I was thinking it might be there under the plastic for the two piece uppers some cars had.

The quickest answer to your question may be to take the plastic off

I had the two piece rear seats, and my 4th gen seat back bolted up perfectly and latches just right... I'd imagine the hole for the bolt may be there, but the threads may not be in place.