The Mach1 shares the same heads, so I've read about the issue as well. The prevailing theory is that the cooling design is flawed, allowing some cylinders to overheat and do nasty things to the valve guides. I've heard it in person once (on a Cobra), and the sound makes me want to cry Luckily, there are preventative measures available.
As for what to look (listen) for... well, just don't freak out and get too anal about it. The valvetrain and injectors are a little noisier than some people are used to. If it really does have "the tick", it will probably be more of an "oh my god, what is that nasty sound" kind of effect. There are videos floating around somewhere if you've never heard it.