The bigger 5th Gen 4Runner (2010-2015) brakes can be installed on the 4th Gen 4Runner (2003-2009). Three main components are a direct fit and size upgrade: front calipers, front rotors, and rear calipers. You’ll just need 17″ or larger wheels to fit the larger brakes. Swappers report better stopping power with the 5th Gen brakes, especially if coming from the smaller 319mm 4th Gen brakes.
To positively identify which front brakes you have, check the brake caliper for the identifying code cast into the side. All 4th Gen Sport Editions and some Limited trim models came with the larger 4th gen brakes. But if you plan to make any changes that require knowing which caliper you have, check the stamped code no matter what trim you have, as it could have been changed in the past from OEM configuration.
The 4th Gen front dust shields may interfere with the bigger rotors. You can bend or cut them for clearance (be careful not to breathe in brake dust, use PPE), or put on the 5th Gen shields. Pics of 4th Gen front dust shield trimming can be found here.
It’s debated whether the 5th Gen calipers are less susceptible to seizing (a common 4th Gen issue). I’ve seen many reports of 4th Gens seizing, and then the swapped 5th Gens not seizing over the same service periods. But there’s likely some confirmation/investment/reporting bias there, and there are reports of 5th Gen calipers seizing, too. I haven’t seen any systematic long-term testing or data, so it’s hard to draw an objective conclusion. Some say corrosion is the root cause of the seizing issue, and that the 5th gen pistons are just as prone to seizing, being the same design as the 4th Gen. As such, some have tried coating the pistons or recommend getting aftermarket calipers with coated pistons to resist corrosion and reduce potential for seizing.
Lots of good reference info on the 4th to 5th Gen swap can also be found here: https://www.toyota-4runner.org/4th-gen-t4rs/249328-5th-gen-4runner-brakes-upgrade-4th-gen-4runner.html