I ran a heavy-haul wrecker once with a chain-driven recovery winch powered by a regular PTO. It's possible the dump bed pump might be chain drive, but I can't imagine much of anything else unless the bed is lifted by some sort of jackscrew. Also can't imagine any Chevy production run of only 100- - - -maybe the dump system was limited-production, but not the truck itself!
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!