when i ordered my SR springs, i had the same issue with panhard being on back order. i went ahead and installed my front springs, and i waited on the rear just to be safe. i received my panhard about 2 weeks later, but haven't had a chance to install yet.
Current: 2015 GT Premium Performance Package-stock for now
Past: 13 V6, 11 MCA V6, 89 GT, 88 GT, 04 V6