Depends on how much work & money you want to put into it. First off, everyone says that their seat is in good or decent condition. But the truth is, 99% of the seats I tear apart to restore, have issues that need to be addressed.
This is why I started restoring seats, wether someone did the work themselves or took the seat to an upholstery shop, seats this old have underlying issues. Myself, years ago, I took my seat to an upholstery shop. I paid all that money and found out, upholstery shops don’t touch your frame. I looked at my seat, and said, OH that looks way better, nice new cover!! But I get it home and turn the seat over and get to looking, nothing else was obviously touched. I called the shop up and they say, that’s all we do, is upholstery. So I called a few other places, which there’s not a lot of, and got the same answer. Upholstery shops only do upholstery. Maybe that’s ok for some people, but not me.
1) Rusty frame is the big one. Let me ask, if you have a moldy wall, would you paint over it and not fix the mold? Most would answer No, because the mold is still there and will resurface thru the paint, so time and money wasted. Why would anyone put a NEW Cover over a rusty frame, seems like a waste of money.
2) These seats always have broken springs. That’s why the seat leans to one side or it’s sagging really bad. I have torn apart seats, that have some major rigging done, instead of replacing the springs.
3) Tracks are hard to slide or don’t slide at all. I’ve gotten seats from people, that didn’t even realize that their seat did slide,
But to answer your initial question, purchase a new seat cover. Take the old cover off and install new one. You’ll need hog rings & hog ring pliers. I guess it’s up to you what you want to do about the rest of the seat.