Some people have asked about the backs of the Z seats and how to fix them. There is only one real way to do this which is to buy new ones or used ones in mint condition.
However, it doesn't mean you can't clean them up a bit and make them nice. All you need to do this is a pair of scissors, about two yards of whatever fabric or material you choose, a roller or squigi, some caulk or filler,a phillips head screwdriver, some tacks and a can of spray adhesive. For very little money you can make the back of your seats look good again. Let's start with the old choppy lookin' seat back as seen below.

Crappy lookin' huh?! That's ok, we're gonna fix 'em up. Get yourself the caulk/filler and work it into the cracks and fill some of the holes. You may have to do this more then once so don't rush it. To smooth it out, use a wet papertowel. Then lay it out in the sun or in your living room whatever floats your boat and let it dry.
After it dries, put in on a newspaper and spray real real good with spray adhesive. Make sure you get every inch of the outside sprayed real real heavy. Once you've done that, slowly start to roll your fabric onto the back. If you want it to be one hundred percent perfect (which isn't reality but you can try), work the fabric around until it's to your liking. You may put a couple of creases into the fabric as I did, or you can score the fabric and seem it so you have no crease whatsoever. Again, this will be towards your liking. Use the tacks to keep the fabric in place on the back of the backs. I used two tacks on the outside as well. Two for each side. All outside tacks were black in this case.
Make sure you roll the lumps out real good or if you live in Florida like I do, you have one really good, cheap and free tool called the hot a$s sun that will do this job for you in approximately 3 to 4 days just as if you were applying window tints. Put the backs back on the seat, screw them back on and alas, you have the finished product.
Like all projects, have fun and enjoy.