Just a note there are quite a few pieces to the Air-Flow so buy as complete a set-up as possible. Here is a picture series for a NOS I owned some years back.
https://www.flickr.com/photos/advance-design_parts_co/8129413707/in/album-72157631868452754/
Another view so you appreciate all the parts.
https://www.flickr.com/photos/advance-design_parts_co/44267047400/in/album-72157631868452754/
Here is the recirculating gear, I still own this NOS set, not as complex but requires the plates to block off the openings.
https://www.flickr.com/photos/advance-design_parts_co/8129444676/in/album-72157631868452754/
https://www.flickr.com/photos/advance-design_parts_co/15838946822/in/album-72157631868452754/
Those flat Delco-Remy or Arkless switches can run $50 and up all on their own if you decide to go OEM.
https://www.flickr.com/photos/advance-design_parts_co/8129352382/in/album-72157631868452754/
This is a rare piece I kept (I should reproduce them), the original Air-Flow hang tag.
https://www.flickr.com/photos/advance-design_parts_co/29739577756/in/album-72157631872034068/
https://www.flickr.com/photos/advance-design_parts_co/29775287635/in/album-72157631872034068/

1950 Chevrolet 3/4-Ton 3600
More pictures on Flickr