how to tell if a truck is an orgional 4WD?

[ggtsvnv]

Hi all,

I have found a 69 GMC 4WD truck for $500.00. It has some rust in the rockers and cab corners and a few bumps and bruises but the rest of the body seems ok. However I'm not sure if it was a 4WD from the factory, the bed and cab have no gap between them at the top which makes me wonder if the frame was switched or bent. Looking under it at the frame I cannot see any obvious bends in the frame so I was thinking maybe someone took the truck and put it on a different frame to make it a 4WD. It does have on the inside roof of the cab instructions for the 4WD shifter (which seemed like a strange place for it). the glove box door is not orgional and was wondering is there any other way to tell if it was a factory 4WD?

Thanks in advance