1970 Duster bench seat headrests removal

I can't remove them......working on the drivers side presently and it seems like the inboard rail is preventing the headrest from coming out. I tried fishing a long zip tie and an old oil dip stick along the back of the rail in an effort to help the rail release but no luck... I don't want to damage the headrest.
Does anyone have a pic/schematic of the headrest system on how to tackle this.
Thanks!