Leaf Springs or Air Shocks for sagging 197070 Chrysler 300

Several years ago I asked an old friend mechanic to help with the tired look of my 1970 Chrysler 300. I was thinking leaf sprigs but he recommended air shocks. I'm looking for advice on what would be best in the long run. Not surpisingky, the shocks no longer hold air. Any advice and hints on what to order and where would be appreciated.
Thanks in advance.
Dirk