Beats me, our 91 cruiser needs new padding. I saw something like it on the tv show "Trucks." They had a kit that included new padding and new seat covers for an older American Truck. Not much help I know, but a start.
You need to remove the seat from the vehicle and take it apart. You will need hog rings and hog ring pliers. If you have never done upholstery work you may want to have an automotive upholsterer do it for you. You could save some money if you removed the seat from the vehicle yourself and took just that in. I just looked at the driver's seat "bun" for a leather seat vehicle (80 series 93-97). That one lists for $131.29. A "Smart Shopper" could get one for around $98.47
since my front seat cover is torn on my 88 fj62, I just took more foam and shoved it under. I sealed it with duct tape and threw on some cheap 10 buck seat covers. Can't tell the difference until you pull off the covers.good luck!
I used enough ductape to cover about 6 inches or more from the tear and I just overstuffed the foam that I found laying around. I would maybe get a higher density foam, especially if you want to get more support around the edges. That way the seat stays in form of a bucket rather that a flat seat.( the duct tape does flatten the edges a little).