Here are some pictures that may help.
https://www.flickr.com/photos/advance-design_parts_co/12647027223/in/album-72157641244124604/Is there some adjustment? Short answer is yes but not a lot. The caution here is the interior attachment to the cowl. That piece will come loose if you twist it and then the only thing you can do is try to JB or spot weld it back in. Your best bet is to do as described in the link or remove the vent door and carefully bend the bracket spot welded to it. In reading your post again I believe the small bracket inside the cowl is loose.
https://www.flickr.com/photos/advance-design_parts_co/8129347797/in/album-72157631868452754/I have actually identified three separate styles of these vents, as a '49 owner you may or may not have the springs but the bracket is adjustable either way.
There was a series of running changes to the vents from 1947-1950 that included springs, levers and lock plates.
Last version, late 1949-1950 pressed handle, no knob, no springs. This last version has no plate, instead the locking notch was now pressed into the inner cowl panel.
https://www.flickr.com/photos/advance-design_parts_co/8129373734/in/album-72157631868452754/Comparison view of the 47 mid-49 handle and the late 49-50 version.
https://www.flickr.com/photos/advance-design_parts_co/8129367190/in/album-72157631868452754/1948 to mid-49 version, maroon knob, straight plate, springs.
https://www.flickr.com/photos/advance-design_parts_co/8129345047/in/album-72157631868452754/1947-carryover to early 1948 version, notched locking plate. Second picture shows orientation on truck.
https://www.flickr.com/photos/advance-design_parts_co/8129342725/in/album-72157631868452754/https://www.flickr.com/photos/advance-design_parts_co/8129368602/in/album-72157631868452754/
