I don't know why it is so important to know but they are typically 1/2 tons. I have loaded a ton without much issue though. That is when the springs are good.
I used my truck to move some wet sand (after heavy rain) from a landscape yard. They weighted the truck before and after loading. The difference was 50lb shy of a ton. I had no problem driving it back.
Ya I've loaded over a half ton of dirt landscaping our yard in my 93 for sure, just make sure to look at the leaf springs and don't load past when they are flat.