Since it's new paint, I'd remove it with lacquer thinner or some similiar solvent. The paint should just melt off. Sandblasting will get grit in between the leafs and make a royal mess, and it will leave a clean, but rough surface. If they're rust-free under the paint you can use Cosmoline to stop any surface rust from forming on the bare metal. A good alternative is to paint them with cast-iron gray paint. Not 100% original, but the springs look nice and they won't rust. My 2 cents and good luck!