popa, as far as I can tell from my paperwork, as far as the 3100 vs. 3104, 3100 is the series (1/2 ton) and the 3104 is the designation as far as body style. (p/u, panel, frame w/o box, etc.)
I may be wrong on this because I am still learning as I go. I am sure smarter people on here will correct me if I am.
