None of the data books nor salesman books make any mention of this option. GMC yes, Chevrolet no. The heavy 1/2 GMC I bought at auction a few years ago, the model 100. You will notice it has 6-lug wheels.
https://www.flickr.com/photos/advance-design_parts_co/8130539722/in/album-72157631870734114/
https://www.flickr.com/photos/advance-design_parts_co/8130511175/in/album-72157631870734114/