I haven't done it, but it has been the rage in heavy duty trucks for the past few years. If I was going to do it on a rod, I'd look into the split tube axle that out there now. Looks like the old Ford twin I beam, only better. I'm just not sure I could do it on a rod.
Doesnt seem like it would be hard. You could use spliot wishbone or front 4 link setup, and have some airbag perhes made to go on top of the axle. If you wantedto keep the bags out of view, you could mount them under the grille(im assuming its fenderless??) or mount the bags to the inside of the frame.
Cenn Penn speed shop sells a kit to do it. The trick is to hide the bags so you don't see them. Clark
Here it is... http://www.cenpen.com/traditionalair.htm It is actually a spring over set up. You could easily adapt to hairpins and a spring behind set up. http://www.cenpen.com/traditionalairorder.htm