Cheap add-a-leafs. Takes a little work, but is cost effective...
Go to the junk yard and find a set of springs and take out the 2nd or 3rd leaf and add them to your spring pack. You'll need longer center bolts, available at NAPA or any decent auto parts store.
Caution! Springs are loaded kineticly(?) and can come apart with bad results if you don't pay attention.
