A lot of the 1st gens don't have tachs in them. I know a guy who's got one with just shy of 450k on the odo. When he bought the truck the dealer told him to shift when the governor says he had to. He would run with a load behind in 4th gear all day, only shifting into 5th when he was empty or going downhill. That engine has never been rebuilt and still gets uper teens for mileage, doesn't burn any significant amount of oil, and is showing no signs of slowing down.
That truck is a '93 1ton dually ext. cab, 3. 55's, 4x4. It was used to haul livestock. It was the first diesel p/u around here, so everyone kinda paid attention to its performance. The rear end got replaced numerous times, clutch a few, transfer cse has never been touched (unbelieveable), rods and mains at about 425k.
So long story short, no, running at 2500rpm shouldn't do your engine any harm. If you have a 2nd gen or custom exhaust on your 3rd gen, it might not be so good for your ears though.