Wisher, then I suggest finding out what kind of security issues they've had in the past, and without throwing the previous occupant of the position under the bus, come up with your own take on them. In that position and in the country you reside in, you probably need to have some sort of views on metal detectors, racial and other profiling, recreational drug and alcohol usage, privacy issues etc. These just from the top of my head, I'm sure you have loads of more ideas.
Also remembering some funny anecdote from way back when with the guy might be useful, but I'd just use it as an ice breaker in the beginning of the interview. Knowing what his former colleagues from then are up to nowadays might be good too. Since you also have a relationship with him, don't be afraid to catch up on his life either, if it comes up naturally somehow.
Also talk about what kind of boss you'd be, and how you would further improve the general mood of the team you'll be leading.
And be ready to give contact information of possible references, they don't always have to be former bosses, for a position with employees some employers might even be interested in talking to a former employee of yours, if you can think of someone who can talk you up in a professional manner.
I'm pretty young to be telling people what to do in job interviews, as I haven't had that much experience at it, but on the other had I've never been to one where I haven't been offered a position.