About 10 years ago, I bought recover kits from Nissan. They were exactly like the original equipment. They are really easy to change. Pull the seat from the car, and unscrew the back from the bottom at the side metal pieces. Then just use some needle nosed pliers to bend up the little metal tabs that hold the cover on. There are a couple of hog rings on the center flap that pulls through the front center of the cushion (it is what gives it its form-fitting shape). The flap has a strong piece of wire in it, and the hog rings holds that piece of wire to an identical piece that gets positioned against the suspension straps (2" wide straps rubber straps that act like the springs in a sofa). A pair of hog ring pliers and new hog rings are nice - but not necessary. You can use pliers on them AND reuse them if you are careful and don't break them.
About 22 years ago the interior of my car was flooded (don't ask, its a sad story) and the seat bottoms got soaked. They eventually dried out, but they mildewed and smelled bad. New seat bottom cushions were not available - the only option was to buy new seats. So I took them apart, and took the foam cushions to an upholstery shop where the guy used them as patterns to fabricate new cushions. They worked, but were nowhere as nice as the originals as the pieces of foam had to be cut glued to approach the nice shape of the originals. They looked fine once the covers were on, but they did not have the comfort or support of the originals. Over the years, the drivers seat has pretty much flattened to a pancake. I put one of those aftermarket cushions on it, but it made it feel more like an uncomfortable bench seat than a nice bucket seat. And now that I am getting older and the ole' bod aches as I arise in the morning, my back could not take the discomfort of the seat anymore. So, 2 weeks ago I pulled the seat and went to work on it.
I pulled off the seat cover (the one I replaced 10 years ago) and went to work on the bottom cushion. I used the existing foam as a basis, and added to it. I used a "Wall-Pillow" (a special neck support pillow available at some drug stores and medical supply stores) to build it up. I cut the pillow down the middle, separating the wide side from the narrow side. I them cut the wide side in half, and turned them onto the cut end and glued them with spray glue onto each side of the cushion. When stood up on the cut ends, the foam kind of looks like a letter "P". So if you looked at the cushion from the front, it looked like (bear with me, I'm not too good at this) Top \)___(/ Bottom \___/
I them took the narrow side and cut it to fit the front where your thighs go, gluing it also so that the curved part of the "P" aimed towards the center of the cushion. After I had those pieces on, it looked like a weird sort of bucket. I then used 3" convoluted bed foam to fill in the center, and 1" foam on the underside. I finished off with polyester fiberfill to make everything taper nicely. When you cut the pillow to fit the foam, you need to cut at angles. Looking at the cushion from the top: \__F__/ | | \| |/ ----- R
You want keep the same kind of anles as the original foam and seat cover have. You need to angle the back part so that it fits into the cover properly and so that you can screw the back of the seat back on.
The suspension straps had pretty much given up the ghost, so I did a number on them too. I got some 2" wide VERY heavy duty elastic and sewed it onto the metal hooks in place of the existing rubber. Then, to add even more support, I used 2 21" black rubber bungie cords. I wrapped them around the top of the frame and hooked them together with their hooks on the underside of the frame - then used piers to bend the ends of the hooks in really good so that I wouldn't cram one into my hand if I ever put my hand under the seat. The worst part was getting my newly fabricated and very LARGE cushion back into the seat cover. After lots of groaning and some mild cursing, I got it in there, pulled the center flap through and hog ringed it into place. All told, it took about 5 hours to design and execute (I also did some mending and re-inforcing to the seat cover while it was off). Oh yeah, I had to add a little more fabric extension to the center flap because I had so much foam in there that the old one wasn't long enough to reach even halfway through my new foam.
The end result is extremely comfortable. The seat bottom gives very good lateral thigh support and thigh support on the front of the seat. It is also very cushy on the old bottom - it fits my bucket well. It is almost as comfortable as the seat in my 300ZX, which I love. The only missing item is the adjustable lumbar support, and I'm still pondering how to imitate that. It didn't cost me anything to do this as I already had the pillow and no longer used it. The labor was well worth it and my hands should be completely healed in a few more days....