The roller lifters are not hi-perf versions and are common to 6-cylinder engines. I know this because the small washer holding the needles in place around the roller axle failed, allowing the needles to fall out (now I know where those mini-washers came from) and eventually the roller stopped rolling. When it did, the engine will still run fine, but the screetch is like a bad power steering pump or failed accessory bearing. You want to get home quickly, because the (non-rolling) roller will wear down and the beating it takes from the remaining cam lobe will mushroom the lifter body and may ruin the lifter bore. I can tell you for a fact that driving 12 miles with a non-rolling lifter is, uh, safe and does not ruin the lifter bore. You should change the lifters as a preventative thing to do. You will not be impressed with the new ones, though.
PS this occurred at around 85,000 miles and had 1.7 rockers from when I bought it at 20,000 miles.