hahahahaha - I'd call it a 55-57 car heater fan and some very creative ducting - makes me think the heater is from a car as well, a make-do farmer who also liked warm feet

iI wouldn't be suprised if the inside heater is a 55-57 car, not the right shape for any year truck heater I'm familiar with, but it does have similarities to the one that was in a 57 sedan I had
unless you're planning on using the truck on the farm, I'd strip alla that stuff off, inside and out, and find a more correct heater, there's some that work quite well
Bill