Rear suspension help?

["Paul" <9laser3@bright.net>]

  My '69 1600 is beginning to show it's age with a bit of sagging in the
rear end.  The shocks are fairly new KYBs.  The leaf springs are almost
level to the ground behind the axel and before you ask, that's with out my
bulk in the driver's seat!  I'm looking for some inexpensive ways to get
back some of that youthful bounce.  And I'd rather not flip the back
shackles.

TIA,
Paul Kort
Ohio