I am wanting to order and install the firestone riderite airbags. In looking at the firestone website it lists part no. 2299 for a dodge 3500 and part 2478 for a 3500 HD cab and chassis. My truck says 3500 HD on it and is a dually but I don't know what the cab and chassis means. When I look at the installation instructions for the 2299 it shows a straight frame which my truck has, the 2478 shows an arched frame. Can anyone help me verify which version of the airbags is right for my truck or help me know how I can tell for sure. The 2299 is a no drill kit which uses the bumper holes which my truck has, but 2478 is a side mount for which you must drill holes.