Search the Internet for hog rings and pliers
and:
Search the Internet for GM upholstery clips (I think they used to be called barrel clips) - these simply got pushed on, over/around the upholstery end/edge.
I have the "C" clips that slide in and hold the vinyl in place on the seat frame, just have to figure out how to get them along the short sides of the bench seat - not much room for tools... But searching "GM upholstery clips" there looks to be a few different options that may work a little better
