There's a guy on FSC (might be on here too) that did his extended cab windows. F'in sick extended cab GMT400 dually slammed on semis, with old school Impala interior conversion and a wood bed floor. I forget his nick.
I think I know who your talking about. He actually has a crew cab and your right, that is one bad dually. Thats who I've been trying to find to give me an idea of where I can get the kit but I haven't seen him around in about 4 years.