I used to own dump trucks that I hired out to the city to haul snow. I studied the heated dump box (exhaust runs through cavities in the box structure) and decided against it because the snow melts at the heated areas and less so as you move away from the heat source. Depending on air temperature and snow consistency, there are usually areas in betwen the hot and the cold where the snow tends to stick and build up. I compared my trucks to others that were heated, and on any one night (we usually hauled at night), the snow could be sticking in mine but not the others, or sticking in the others but not in mine, depending on temperature and snow condition.
Anyway, that may or may not be relevant here. Something to think about.