I completely do not understand your theory on why you would want to use old stuff when new stuff is available and free?
At his requested performance level the 6.7 parts won't do anything for him power wise. That being said holding the old flimsy 5.9CR parts in my hand VS the 6.7 parts, hands down I want the new stuff.
Get an aftermarket 6.7 intake horn and use 6.7 plenum/rail parts, unless you're extremely cheap and determined to show what you can do with old parts even though you had new parts for free at your disposal. Or.. use stock 6.7 horn and spend $69
2007-2012 Dodge 6.7 EGR Delete - EGR Delete Kits