If you mean why doesn't the CUCV have dash vents in the front, it's because they were a base model truck without A/C.
To add the dash vents, you would have to cut out the mount for the dash mounted bracket, then you would have to get a plenum box that has the heater side mounts for the vents. I'm not 100% certain, but I don't think GM had a heater only version with the dash vents so you would have to get an A/C box and modify the firewall to mount it properly.
Later,
Joe