I say they both fits. Same size. Only difference is the limited stereo has an amp right behind the stereo. You can also use Subaru stereos. I have a subaru 6 disk changer attached to my toyota (different wiring plug but same number of wires). All the stereos in toyota's and subarus are made by the same fujitsuTen.
All toyota (lexus) stereos have 10 + 6 wire harness. The SR5 stereo has 10 + 6 pins at the end of the stereo, so it plugs right to the main wiring. If you are using the limited stereo, the main stock wiring 10+6 wire connector will go into the amp and wire plug from the amp is going to the limited stereo. It is that easy!