Three more images, just because I can.
I've got a '55 with a bench seat but it's powered, no help there.
This white manual bench seat is from a '57 Bird, hope it's close enough to what you have.
Right-side up this time, looking at the drivers side, inside of the seat track.
Photo 1, The attaching point of the rear of the spring on the seat cushion frame.
Photo 2, The attaching point of the front of the spring on the lower part of the seat track.
Photo 3, upside down again, a re-do of the other photo, at the front drivers outside of the lower half of the track assembly. Showing the hooked front end of the spring, at the Yellow arrow.