Finally found the dead mouse that's been stinking up the car. It was found in the passenger side of the windshield cowl area. This is one of the areas of the car where fresh air is sucked into the cab. This is also the area where the water naturally drains out of the cowl (base of the windshield) after it rains or after a car wash. This is also an area where years of pine needles and the usual debris collect and pile up on both sides of the car. Unfortunately, this tends to pile up under the windshield wiper motor, which happens to be on the pass side of the cowl. After this pile builds up and doesn't empty itself out, moisture tends to accumulate and you may have rust issues. Thankfully I live in NM so I only saw dampness from the last rain as we're in a monsoon season right now.
Just so everyone knows, the ENTIRE cowl area that's under the windshield and behind the dash is open from left to right. So, if you were to shove water through a garden hose on the left side, water will come out of the right side and also fall into the fresh air vent
So, don't do this but just letting you know how the air flows.
Removal of the cowl is a minor PITA but well worth it to clean this area out. I followed the FSM instructions and they were pretty spot on.
Additional debris was found INSIDE the cowl where the lever to rotate the driver side wiper arm resides. Mouse has been building a nest using home insulation in this area for a long time. Anyway, lots of vacuuming later, everything is clean. Now, I'm going to find stainless steel wool to stuff everywhere and to put window screening under the plastic cowl grating (that you see normally).
I wish it was easy to block this entire passageway out with using window screen or chicken wire. However, due to the driver side wiper arm linkage going in/out of the air passageway, I figured SS wool might be a viable option but I'm open to ideas.