The antenna on that Chevy appears to be mounted to the tool box. That's a fairly common way of doing it. It isn't bad by any means, if it's done properly. It all boils down to 'where' it is most convenient, not a huge hassle to work around.
Mounting position can certainly make a difference, but in most cases, that difference isn't going to be a super 'biggy'. Antennas tend to like being above metal more than beside metal, and definitely don't like being under metal! That's a 'ROT' (Rule Of Thumb) only.
If you think one particular place is better for you, then give it a try. Nothing says you can't change it later.
- 'Doc