As others have written the Heater Valve Repair Kit worked great. Specifically, it solved my problem of the system blowing hot air even when the temperature controls were set to max cold. Heat temperature settings worked fine, as did A/C. However, I just got hot air when all I wanted was outside air blown through the vents.

A few notes for others who will undertake this repair:

1) The old washers and gasket looked ok, but they clearly were worn after twenty years.

2) The repair kit includes extra parts not needed in the M-B/Crossfire heat valve. AMHIK. I have "X"-ed them out in the image.