As I recall, the crank mechanism bolts to the underside of the dash. The "strap " you are referring to screws to a hinge that mounts to the center window frame at bottom. You will need to free up the window frame to get it out. Chances are the rubber gasket in the window frame is junk anyhow, so you could cut around the frame to release it. There is a good " how to " post in the tech section, covering rebuilding the regulator.

1940 Chevy KC 1/2-Ton
In the Stovebolt Gallery