I just installed a CB antenna on my libby, and I have a few thoughts for you:
1) Make sure you get a good 18' - 21' coaxial cable. I had a 12' cable which was the perfect length to reach my CB, but I have been told by numerous truckers that 18-21' is the ideal length (and my SWR dropped substantially when I put the longer cable in)... again, I am no expert, but I wasted quite a bit of money trying to get a good setup that works for me.... and it works for me...
2) A few people here are stoked about the Firestik II, it has a little nut on the top that will let you tune it. If you do go with a fiberglass antenna, MAKE SURE IT ISN'T THE "CUT TO TUNE" . The Firestik II will have the cap removed so you can see the tuning nut on the top. I found a 4' Firestik II at a Pilot gas station, they seemed to have the best selection.
3) There is a rear antenna mount available thru kilby enterprises for around $60 or $70. I made my own post by turning a chamfer into the end of a piece of 1" bar and tapping the end 1/2-20. I then used my clamp style mount to clamp it to the post. I will be able to take and post some pictures of my latest setup tomorrow.
4) the only problem I have with the setup listed above is that I have a roofrack, and I feel like I am not transmitting in front of my jeep, I could be wrong, but firestik suggests you have at least 60% of the antenna above your roofline.... I am somewhere between 40 and 50%. I also ran a #12Ga ground wire to my trunk hindge. (I will take a picture of the install).
5) Some people have complained about fuel pump noise from mounting from the spare tire, I can't complain, but some have.
6) The radioshack SWR meter is $50, they sell them at pilot for $20-$25, I don't know how good they are.... but they are waaayyy cheaper than ruining your CB due to high SWR (I guess that if the SWR is too high, your antenna is not able to transmit, and it reflects your transmission back into the CB and burns it up)
7) I paid $25 for my 4' firestik II

I like the look of the firestik, and their tech support on the phone was relly great. Everyone will have their own opinion, I'm new to this, and it's all fresh to me, and that is why I am making such a novel.
9) Here are some pics of my firestik on my roofrack, I moved it because I didn't have a good ground plane, and it was too high (no drive thru's and I hit every tree in my driveway)
Keep in mind I will post pictured of my newest antenna location, and some more detail on the mount tomorrow
Also, I am no expert, but I figure that this is a good time to post my experience to try and save you a couple of bucks.
-Mark