What kind of spring is it? Extension spring like a carb return spring? 160 of anything is a lot of money, throw it away and get another seat. Nostalgia does not require the actual seat, just the correct seat from 55-59. Especially if you use the rest of the seat, the back, the frame, the sliders and feet. Find a good donor seat and reupholster it. Cablesmill is your man for that. Good guy.
Saw your pics, nice work you are doing.
You don't have the original tires either.
