I'm home from Purdue for Spring Break this week and decided to do some experimenting on my HVAC system. I removed it last summer in an "I want to be cool" moment, and regretted it the first time it rained. What I really wanted was some way to:
--Keep defrost
--Eliminate extra HVAC piping
--Eliminate the AC condenser
Here's the original:

And the trimmed down version (heater core cover not shown):


The second pic shows the wedge shaped piece I folded to allow air to flow from the blower motor toward the heater core while not having a gigantic bulge in the engine bay. The defroster works excellently, and is just what I wanted. Total weight savings comes to 15 pounds by the bathroom scale. Made for a decent little weekend project.