This is an manifold designed for naturally aspirated, the best inline design IMO. It's a 4 cyl, but just add a couple more velocity stacks & its for a 6 cyl.

http://www.bing.com/images/search?q=turb...electedIndex=11

Try & make something similar, but your velocity do not need to be offset side to side, they can be all in a row & the velocity stacks should be raised up from the plenum floor for best flow.

Also note is has a tapered plenum, larger in the front & gets smaller towards the back cylinders.

Note the short runners. Something you should go with.

Something of what your "D" plenum should look like w/raised velocity stacks.
http://www.bing.com/images/search?q=turb...lectedIndex=240

12 port SDS EFI