Kevin,

Here are a few threads with discussion on upholstery kits/parts and the "barrel" clips (also follow links in those threads).

Note carefully the need for one more layer of material (that Jim Carter omits).

https://www.stovebolt.com/ubbthreads/ubbthreads.php/topics/1232638/seat-disassembly.html
https://www.stovebolt.com/ubbthreads/ubbthreads.php/topics/1229050/54-3100-bench-seat-clips.html

The "barrel" clips are a royal pain to remove, and to install.