That looks like a decent first truck. In the picture showing the inside of the bed it looks like the back of the cab is dented.
The bed wood is incorrect, but that would be a great project for your son.
The straight 6 and the 4 speed is a pretty bullet proof combo, just right for a 16 year old...
Check it over real well for rust and bondo. Take a camera, and if you aren't sure about things come back here and post pictures of the questionable areas.