There are plenty of people running 3 cores with a mechanical fan and one of the shorter, aftermarket fan clutches. I ran a mechanical fan on my Duster for a while with the Champion 3 core without any clearance problems, although I wasn't running a fan clutch just the straight direct drive fan.
It's just worth taking a look at before hand so you know ahead of time if you need to change something. But even with the 3 cores a mechanical fan with a clutch can be done, there's that "jaguar" fan clutch people used before, as well as the new Hayden clutch