You should call up the guys at tss-radio.com. They have a vehicle specific mount. Ford F250 Super Duty 2008 Custom Mount
These guys are great I've dealt with them several times. I always ask for Matt when I call up, but all of them are great. I've used these VSM mounts in a couple of vehicles, and those cheap crappy mounts they include with the car kits don't compare. If you take a little time, and carefully route your wires, it will make a super clean looking, solid mount that you will like a lot. If you like that, there is a guy around the sat radio forums who can make custom cables to connect your factory sat antenna to your SL100. Hope this helps.