I have installed a Vintage air HVAC setup in my 69. Since these aftermarket HVAC systems do not have an 'outside air' option I am trying to decide if I should retain the factory fresh-air box under the driver's side dash. On the other hand, if I replace it with a plate that would make a convenient place for electronics, etc. So, anyone have good or bad experiences retaining the fresh air box? Or should I simply open a vent window when I need fresh air?