Yeah, it is when the selling price is $2,000 or less haha. That is pointer which indicates the truck might've had a harder life than most. Doesn't help GM put it in a stupid spot, if it had been put on the other side of that compartment they would have held up much better.
Good job on cleaning that, I haven't found something which is aggressive enough to remove the schmutz but gentle enough not to take the ink with it. I spy "GMC", your truck started life in Pontiac, MI. I'm kind of partial to trucks made there or in Flint. I also spotted "GT4" so your truck has a 3.73, or it did from the factory. No G80 though. Guess you could try the ole, "Mark the passenger side tire & then mark the pinion, then rotate said tire twice and count how many times the pinion crossed the mark" method to approximate the gear ratio. If it's close to 3.73, your truck could have the original axle. Every one ton truck I've seen has had a full floater. I've only seen one ton vans with semi floaters.