Hi David;
I don’t know for sure if this will help, but the seat rails in my 1960 Comanche are held in position by screws. Back out the screws and remove (and replace if necessary) the seat rails. There are nut plates under the floor so there’s no need to get under the floor to hold nuts to secure the screws.
I looked up the seat rails in the parts manual, but it didn’t give a spec for the fasteners.
