porterbuilt air bags

[c20pickup]

saw some air bags on porterbuilts website for the 67-72 rear end with coil springs. only 400$!! seemed pretty cheap to me, all it does is replace the coils with air bags and gives you all the necessary hard ware to mount it up. I was considering buying these, except my truck is 3/4 ton, not half. the description on the website doesn't really specify if they can be used on the 3/4 tons. any info would be great! not looking to slam the truck, or lower it much at all, just want to give it a somewhat factory stance, maybe dropped 3 in the rear and 2 in the front. I hear porterbuilt mnake sgood stuff, also what about the fronts? the air bag kit for the front? or the tubular control arms? any info would help!