I'm running Proline 6063 rear powerstroke springs on the 103 g-made piggyback shocks. You can get the spring assortment with firm, med, soft. I bought the rebuild kit as well and you can run the duel springs. All you really need is the slider. Works great and looks good too. I think the Proline soft spring is softer than the g-made soft springs. Just another option.
'Pony