Here's my take on it.. if it's that cool, then he should buy it now, then there's nothing to be paranoid about.
From what you described, it definitely isn't a factory built truck, and more than likely something that was done as a after market conversion for a particular purpose.. like railroad, coal mining, that sort of thing.
I've seen some pretty weird crap done to trucks to make them suit a particular purpose.. and that's probably what your buddy is looking at.
Custom mods and conversions done 40+ years ago DO look pretty 'factory'.
