>>>Third, my van has no fresh-air fan -- not even a switch.  Was this an
>>>available option in 1980?

The fresh-air fan was invented at the end of '80.  My '81 has it
but my VW manual for '80-'81s does not mention it since it was
apparently not really updated....

The Bentley shows both kinds and maybe you could see the
differences.  I suspect you would have to swap the air distribution
box to one with a fan to get the best conversion.

                                Richard A. Jones
                                Boulder, Colorado
                                '81 Vanagon  Mr Bus