Dingus,
That looks something like an ABS tone ring, not something normally found on these trucks (86-94). What year is your truck?

Having said that, I would imagine the tone ring is just pressed onto the hub after the rotor is in place. And if you can find away to support the hub, and press off the rotor and tone ring at the same time, you'd be in business. It looks like there is a small gap between the ring and the rotor, can you fit a 2 or 3 jaw gear puller in there?