hi Gray_Ghost recently took some photos of fixing a seat for one of my truck this summer, attached a few photos of the clips in action. the original tiny metal clips are spring steel, they will stretch a lot if you need clips i suggest a trip to the wrecking yard, i took all the clips off a couple seats and cleaned them all in evaporust liquid overnight so that i would have plenty of good ones to pick from when reassembling the seat. the grey material i used is recycled school bus seat from a bus i bought to use as a storage shed.
i suggest you do a test fit with a small patch of material to see how it goes before committing to the whole project, just push them down with your weapon of choice, i put one about every 3 inches or so. don't forget to preload the seat a bit so the material is snug, i put my seat in a 20 ton press, but barely loaded it down. i hope this info helps, please send picks of your work! -s