Jeff, I'd agree with Miles--a hamstick or similar is an easy and cheap way to give HF mobile a try! A lip mount or a bumper mount, or something similar, is a good starting point. (You may need to run a ground strap from the mount to your car, despite the mounting screws--I almost always do, too.) The standard 3/8x24 mount is very convenient for later experimentation, and you can use it for all sorts of antennas, so it never hurts to have one on your truck.
If you haven't seen Alan's website, look at www.k0bg.com
and look at LOTS of examples of antenna and radio mounting.
As Miles suggested, you don't need anything expensive or fancy to get started and give HF mobile a try! I've got a link to my mobile setup from my qrz page; my mobile antennas are cheap and work well for 20m and above. Give it a shot--it can be GREAT fun to work HF from the car! 73 GL! --ken