Not sure you are aware but you can buy upholstery sinno wire also know as zig zag wire. Get a bag of BW clips and a crimp tool and your in business. If you dealing with a few broken springs, it much easier to repair then most think.
I basically rebuilt a bench seat for my tempest. You can find my writeup in the Interior Tech section. This is a great resource.
https://www.hotrodders.com/forums/interior.20/