I prefer the Uniden PRO-520XL to that Cobra, only because the Uniden has an auto noise limiter circuit in it. It's $9 more than the Cobra.
Uniden PRO520XL - Amazon.com $49.99
If you're only going to ever use it wheeling, buy one of these, throw it on the middle of the hood, and call it done.
Wilson Antenna - Little Wil' - Amazon.com $36.18
That's exactly what I've run the past couple of times out, and it works great for talking on a trail. You'll have to cut the whip to length to tune it the first time, and after that it's plug and play.
It is not an "ideal" installation, in that it uses 18' of coax as a counterpoise for the radiating element rather than having a proper ground using the metal structure of the vehicle. This has a negative effect on the efficiency of the antenna system and creates some RFI in the cabin. It'll work ok though, and at 4-6w the RFI isn't anything to worry about. I sure as hell wouldn't run a CB amplifier like that though.