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The light-duty trucks (the shop manual doesn't say how light) used vacuum wipers so that's probably what you have. The heavier trucks used an electric wiper motor (again, the shop manual doesn't say how heavy the truck must be before you could get electric wipers).
If I recall, the cabs are the same for most of the light and heavy-duty trucks so the electric wiper motor from a larger truck may be a bolt-in replacement for your vacuum system. The major vendors also have replacement electric wiper systems for your truck but they run from $150 to $250 or so.
My 56 Car has a electric unit from Dennis Carpenter, neat setup with factory style switch. Also my son has an extra unit from 76Bronco he wants to sell, it replaced a vacuum unit from the early models that mounted ontop of windshield.
Dustin, my Hollander interchange says that wiper motor -part #COTF17508A - will interchange with 56 to 60 1/2 ton thru 4 ton trucks except panel delivery and tilt cabs. Randy