Please Help with this 1981 GMC

[gcm]

I found a fully loaded 1981 GMC Sierra Grand which looks to have a factory conversion of some kind. It looks like it has the same treatment that the 70s and 80s vans use to get with some decals and more comfortable captain's chairs. They seats look like super comfy bucket seats. Do you guys think this is a factory mod and is a super rare truck is it worth buying? It will need some body panels and cab corners. It runs and drives.