This was a very common practical conversion in farming communities after the newness of the Model A had worn off and secondhand owners took possession of them. It happened to Coupes, too. Some conversions were done more skillfully than others. I have seen some really crude ones, as well as some that were nicely done with care and forethought. If you didn't know they were not available like that from the factory, you'd never guess they were conversions. There were advertisements for boxes that fit the Model A exactly, including installation instructions. The availability of such conversion boxes re-purposing the Model A is another reason so many of our beloved cars survived, while other marques found their way into the blast furnace.
Marshall