<VV> CORVAIRS WITH DUAL HEATERS

[shortle]

It seems I have seen a few Corvairs over the years (early models) that came equipped with the gas heater option AND the direct air heater option. A guy in Arizona has both on a Greenbrier, a guy in Colorado (not me) has both on a Lakewood and it seems a guy in California has a 4 door Monza with both. Can anyone enlighten me on this configuration? Again, we are not talking late models.
Timothy Shortle in Durango Colorado 81301
Going to the Fan Belt Toss tomorrow morning