I replaced a few springs on '37 seat bottom, a local shop had a some used ones on hand he let me have. I used wire ties to hold it all together, I couldn't find any metal retainers that would stay in position. The wire ties worked pretty good, just put the "knot" towards the inside of the seat. Mine also had short pre-bent wires ( spring steel ) linking all the springs together, I used heavy twine to replace the missing links. The links make one spring pull on the others so it all moves as one. I have since added thick foam along the front edge, I just shoved a couple pieces up between the rows of springs. Mine would sag at the front edge giving no support, felt like I was always sliding forward. The heavy foam is rigid enough to keep the front up so its somewhat like setting in a bucket seat as the rear is still pretty soft. Before adding the first layer of padding, I secured a layer of vinyl over the springs, this kinda leveled out the old springs and keeps the padding from falling into the springs. I'am pretty happy with the ride.
I talked with a shop about changing over to all foam but still keeping the same shape and fit. It was going to be expensive, they would use 3 different foam densities glued together and hand carved where needed, then covered. Thats when I shoved foam into my old frame and springs, a much cheaper option !
