Bears63, looks like I was mistaken about use of the hydraulic clutch, I could have sworn that I had seen that 4x4s used the mechanical clutch. I just checked the '60 manual, as well as Moses Ludels Chevy and GMC Owners Bible, both agree wit what you said. Ludels book also states that the hydraluc clutch was used in the 4x4 to '63. So it could be a '60-'63 Chassis. I am inclined to think that it's an earlier chassis, the later GMC 6 cylinders used a 2bbl carb. I would have to check a bit further to make sure whan that change was, though.

Bill Burmeister