Hey Dr Miller, Welcome to Ecomodder.
I think you'll find in this forum most people are not too worried about what you do in the front of your project, just so long as it is a rounded shape. Rather, you'll want to focus your attention on the back of the project, what does the air do after reaching the widest or tallest part of your trike. You'll want to strive for following the ideal aero dynamic template from the highest/widest point back.
I think initially ducts would be better if you can make the suspension aerodynamic. If you have a bunch of stuff hanging in the slipstream that is round, that will not be optimal. Also you need to consider the level of difficulty when building fairings/fenders vs a single piece body. You also need to consider what the motivation for this is. Is it Style? or is it Aero and MPG Efficiency? In using a 1500cc engine, I'm guessing optimum fuel efficiency is down the list a few points behind acceleration performance. By "enclosed" do you mean bathtub or fighter jet?
This looks like a good idea to start with here of all the stuff I looked at.
Anyway, this looks like fun!! I'm certain you'll have no shortage of help in here for aero support.