The standard plenum doesn't have that much clearance past the end of the air intake runners, so unless the trumpets are longer, something like that with less clearance to the trumpets should be possible.
Maybe starting with aluminium sheet as a backing plate attached between the throttle bodies and the trumpets, and then fabricate a box containing a circular inlet that will fasten to this.
Ideally you want to feed cool air in from a high air pressure area such as through the grille.
If they will fit a DE, I'd use two 350Z HR air-boxes and then connect these to the boxes surrounding the trumpets.
The HR air-boxes could then be fed by something like the EVO-R cold air intake. See my efforts on my DE:
http://s12.photobucket.com/user/GrahameJ/media/IMG_2404_zpsvx8xzzzi.jpg.html