Here are some pix I made of the sway bar bushings and nut on my stock 73. The top "nut" is actually like a "plywood nut" used in woodworking to secure panels with bolts, it is fabricated from sheet metal with a threaded cylinder attached.
Note that the sway bar is sandwiched between the two rubber bushings and not in direct contact with the top nut.
Theres also a pic of the underside of the mounting plate for the bolt secured with 2 bolts into the lower control arm.
On my 73, the bolt that secures the sway bar also secures the radius rod to the lower control arm. It is "splined" and press fitted into the radius rod. So removal is a real chore and may require loosening the radius rod and or unbolting it from the control arm. Part of the bolt extends downard thru the control arm and ball joint mount and secured with a nut, the other end extends upward to secure the sway bar.
I suppose that if your bolt was rusted, and you cannot find another it would be possible to replace the bolt with allthread and nuts below the control arm and one above the radius arm, then secure the sway arm and bushings with a washer and nut at the top. Best to use a self locking nut or jam nuts so you can compress the rubber bushings to the proper tension.
Also, I think you might need to weld the bolt onto the bottom plate to prevent it from moving around.
Also note that there is a spacer between the control arm and the bottom washer holding the rubber bushings.
I also included a pic of the sway bar to frame mount for a stock 73 if you need it.