you didn't say if it is the complete seat or just one part. but
Valiant(convertible )Bottom seats are different than the dodge convertible variety. You can use the springs clips from a sedan or hardtop of the 63-66 years (probably later years too) to repair the springs on the valiant seat seat. the convertible seat backs looked to be the same internally.
dodges go all the way down into the footwell and valiants go to the riser top
this shows the valiant one that has a straight bottom and also the springs 'n' things. View attachment !!!!rear seat valiant.jpg
you can get new replacement springs if you need them
Grab a 63-66 4door seat and gut the goodies out of one of them to repair the valiant one grab a set of hog ring pliers and some hog-rings if your repairing them, replace the burlap with good quality Canvas and hog ring the wire cross listings to the springs and canvas in a few areas on each spring to help spring movement(plus it feels better too!)and easy wear and tear.
don't weld any of the spring wire(it'll go brittle and break) just pick up some splices at a trim shop or online. Use the hog ring pliers to crimp the (2) splices onto the broken spring and the overlapping new spring.