Are you sure it does not have 8 lug wheels? I do not think Dodge used any 6 lug wheels in 1984. Some of the later Dakota trucks had 6 lug wheels. None of those are 1 tons though. Some of the really old (1930s or 40's???) Dodges may have had 6 lug wheels. If if does have 6 lug wheels and it's a 4x4, someone probably swapped Chevy axles under the truck.

In regard to the VIN number, in some years there was a digit in the VIN which denoted a GVW range. In other words, this digit would identify the truck as being between a minimum and a maximum GVW limits. Having the GVW range may, or may not, help you to determine whether or not the truck was originally a one ton. If the GVW range is high, then it is probably a one ton. If it is a lower GVW range, the truck could have been a 3/4 or a 1 ton. Often times, there is little difference between a 3/4 and a 1 ton truck.