It’s a 1981 through 1985 model
When the Series began they used a 1981 model truck. As the TV-Series progressed newer model trucks were brought in.
In some episodes the truck is clearly visible as a 1985 model. The front bumper magically changed from the wrong model
year to the correct model year.
I think he would have a GMC Sierra, a Chevy Silverado or Colorado, a Dodge Ram or Dakota, a Ford F-150 or even a Toyota Tacoma or Tundra, a Nissan Tundra or a Honda Ridgeline!