The cowl vent handle attaches to the door and the door attaches with two screws to a bracket spotwelded to the inside of the cowl, see picture.
http://good-times.webshots.com/photo/2112021580102454676sQbfdW

The next picture is how a 49 looks inside, 50 does not have the plate or the marroon knob on the arm but is pressed steel.
http://good-times.webshots.com/photo/2126241870102454676QNMKQo

Next picture is of the entire 47-49 cowl vent pieces.
http://good-times.webshots.com/photo/2261760620102454676QYmpkn

1949 vs. 1950 arms http://good-times.webshots.com/photo/2232508520102454676vCeTjM