In my Ranger, I have carried about 1800 lbs. The springs weren't bottomed, but the front end was a bit light. I drove consertively and it handled OK (no sudden moves allowed) and kept the speeds below 60. Like you, I was hauling pavers, so it's not something I do every day.

Having said that, I have a 4WD, so the springs may be a little stiffer. I don't see why you couldn't load 1500 lbs. If these paver are as heavy as the ones I hauled (19 lbs. apiece), you're going to need more than two trips for 500 of them.