Welcome.
Step 1: check the vin on the title against the tag on the truck. If they don't match, run for the hills.
Step 2: Those look like 6 lug rims. A one-ton would not have had those.
Step 3: I am pretty sure the one-ton had wider fenders than the smaller trucks, but that might not be universal
It would not be uncommon for a cab to get swapped and move the vin from a larger truck to a smaller frame, but make sure the vin on the title matches the truck.
A lot of older trucks were titled based on the engine serial number, which makes them extremely hard to legally title if that engine needs replacing for whatever reason.
As far as what it is worth, that is something you have to decide for yourself. You can look at auctions and other trucks for sale. Combine that with what you are willing to pay to decide what it is worth to you.
Things to consider for the value to you:
-Are you going to leave it basically stock or modern it up?
-Are the brakes, steering, and suspension in good condition?
-What is your long term goal? Fix the body and paint? Enjoy as-is?
The more work you intend to do to it, the less it is probably worth to you as-is.
