Taller tires.....New/re-arched springs. Cal-Trac's will raise it an inch or so as well.
This is what air shocks can do to a shock crossmember:
View attachment 105051
My '69 GTX suffered the same fate. Back it the 70's we put air shocks on everything, but they were a PITA to keep properly inflated.(Never had a set that didn't leak)
... oh yeah, and the ride is stiff and obnoxious.