[slotard]

Do you know what trans? My best guess is 700R4, which I don't think was around until 82, so someone swapped it in. It's a little on the light duty side for a 3/4 ton. Did it drive fine when you bought it? Have you checked transmission fluid level? Is it possible you have a drum that's a little seized or something (see if you can roll it easily by hand)?

I have those same years on mine ('73 C20 CS), they flip in to make it not quite so outrageously wide.

Does it still have the build tag with all the RPO codes? If so, you can confirm Camper Special based on that. Or, the badge behind the door might be tent shaped, which means CS. Your rear end appears to be a 14FF, if you post a picture of your spring pack I can look at it vs mine to confirm CS.