10mm head bolts/washers. you can reach your arm up in there, feel around to place the socket on the bolt and remove...
I just removed mine a few days ago and reached in from the top, like a gymnast getting it that way...lol...
here are the part numbers of the seat bottom and top.
269-000-167
204-610-264
the challenger 1800 seat back doesnt have the side pieces attached like the single engine model.
my rear seat bottom may have come from a 97 challenger 1800 as the plastic base was different, but fit perfectly...
either way the part numbers don`t cross over to your boat...