The axles have the Rockwell Standard logo which should make them 1958-1966 vintage, at least that's when the company was called Rockwell Standard. I haven't looked really close but there are no obvious signs of the frame being spliced to make it longer. This truck was originally purchased by a power company and it had the tandem axles at that time. The guy that I spoke to wasn't there when it was purchased but he remembers the truck and when it was replaced by a mid-70s model that was also a 6X6.
