i have the JRS 4leaf springs with the KYB gr-2 shocks. a little lift - maybe an inch - and a stiffer ride would be nice.
i would add a leaf to that spring pack that you have. that should lift and stiffen it. its also allot cheaper than buying another set of leaf springs. you can use your old leafs if you still have them or gets some leafs from any vehicle that has the same width. get some new center pin bolts that are long enough for the added leaf. you can try different length leafs in your spring pack. you can even get thicker ones out of trucks to get a stiffer spring. i dont know how it works with salvage yards in Germany but here its no big deal to go find and get leaf springs in them.