We are mounting my intercooler in the front of the truck in the lower bumper part. It'll be nice and visable for all to stare at.
We use Garrett cores and build the end tanks ourselves. I can get you the size core we use tomorrow. It is pretty much an exact fit. It's good for 1200hp. I believe.
If you're running a rear mount turbo system, an IC isn't really needed. Chris B's twin turbo monster isn't even running an IC. Pretty crazy if you ask me.