In some respects, the date of the announcement probably takes a back seat to the date when first production version of the engine was installed in a car, namely March 10, 1932.
As noted above, the early ones were often short lived. In fact, the first 4,249 were recalled for various changes, many of them major and Ford insisted that those 4,249 passenger cars be placed in service as demonstrators (once "fixed") and not sold as new cars.