I don't know if there is any difference between the head unit for the Sirius and the XM, but I mounted my Sirius head unit behind the radio. There's a little ledge looking area behind the radio and I mounted it there, running the cable under the passenger side dash to the passenger side plastic kick panel (where a bunch of relays, etc. are located) and mounted the antenna box there. The antenna wire can then be routed wherever you plan to mount the antenna. Unfortunately I didn't take any pics. Good luck with your install.

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2007 Tundra Limited Double Cab 4x4 Super White
Key FOB Tailgate Lock (courtesy of Toxarch)
OEM back-up camera w/flip down monitor
Sirius Satellite Radio
20" OEM alloy wheels
Line-X Bed liner
UWS Black Powdercoat Low Profile Toolbox
JC Whitney Black Nerf Bars
Lund Interceptor II Bug Shield
Tekonsha Voyager Brake Controller