I still used my 64 as a truck so I went with the drop springs. I'm still having bad memories of using airshocks back in the 80's so I won't consider using the airbags. If you need more of a drop than springs will give you, they make drop spindles that will give you a few more inches. You may may want to pick up a copy of Classic Truck or Custom Classic Truck magazines, they run tech articles on lowering older trucks all of the time.
Good luck,
Scott
