The dealer (san jose, stevens creek) installed a sirius satelite radio to my GX470 yesterday. Here are the part numbers:
517 IS (not sure what this line is about)
1. PTS31-00052 Receiver Sirius
1. PTS31-33051 FITK, Sirius, ES M
The receiver was installed in the front inside the windshield next to the rear view mirror. The control is through GPS (another source of audio, so i now have AM, FM1, FM2, SAT1, SAT2, SAT3, CD, DVD). Receiption wasn't too impressive. I got "no signal" when the car was near and facing a building.
In response to another inquiry, I don't know if this free Sirius radio was offered by this dealder only or not. However, I didn't hear other local dealers mentioning of free satelite radio when I was shopping for my GX470. You may want to check Sirius website or call your dealer directly.