On the bottom of the stopcock is a 6-sided 1/2 inch bolt head.
Actually it was a 7/16 head. I stuck a socket on it and the gas cock turned right off. The gas tank was the last thing I had to remove before removing the cab.
Save for removing the right running board, which a PO had welded onto one of the supports, all the sheet metal has been removed from the Blue Funk's frame.
Thanks for all the pics and info.