Fwhitetail, I had Firestone airbags installed in January while we were in Savannah, GA. I don't think the place that installed mine were the cheapest around but they were highly recommended as a quality installer. We have an '05 Ford F250 crew cab 4x4 like yours. Total cost including labor and sales tax was $723.62. That includes an onboard compressor with controller and gauge in the cab. Back in April, 2002, I had the same thing installed in our '99 F350 while in Elkhart, IN, and it was $550 and change.
One advantage I'm finding with the airbags that I hadn't thought about is the ability to fine tune the ride when on pavement that gives you that herky-jerky motion. That only works if you have the compressor and controller in the cab, though.