In 48 I think....the gas tank was under the bed, THEN in 50 they got vent windows on the doors. Thus, I think this is how I figured out a few years back that my GMC flat bed is a 49. It has the gas tank behind the seat, and windows on the doors are one piece with NO VENT windows. I found a webiste waaay back taht had the history of these in order, with pictures, with explanations of changes each year. I saved it and then my PC got a virus and as far as I know I don't have it anymore. But that is what I can remember. Good luck.

Whether you think you can or can't, you're right.

Also--in 2004, I invented the spotting alert network in stovebolt after seeing so many trucks when driving around. So that means I am cool.