Find a parts store that has real catalogs and not just computers!!!! They should have a parts book that lists spring by the configuration of the ends, their rate, diameter, and length. Then it's a matter of finding a spring with the same ends, more height, and a softer rate. My Napa guy and Car Quest guy here locally have both been in the parts biz for years and have copies of these "good books"..... Don't bother with the likes of AutoZone and other chain stores, if it's not in the computer they're clueless!!!!