[frankc]

Javadog,

It's actually just the "caps' on the control boxes that are different between A/C and non-A/C setups (see the pictures in my first post). Unfortunately, one is unable to purchase the caps separately - at least from the supplier - as they come as part of the control box assembly. The difference being that the non-A/C setup taps the airflow for the L & R dash vents from the top of the control boxes (diverting some air from the windshield defroster vents), where the A/C setup taps the airflow for the L & R dash vents directly from the A/C evaporator blower.

I was lucky and found someone selling some used non-A/C control boxes that was willing to sell me just the caps.