The column shift cars from 1940-1954 do not have a top cover on the transmission. Just a side cover. I suppose you could use a truck 3 speed case (only) to convert to a floor shaft. On a 1939 it is a different story.
So I guess the next question should be, "Was it converted to floor shift by adding a shift kit or by changing transmissions to a top loader?". If the latter, you need to change transmissions and get all the linkage necessary to put it back on the column. If the former, you just need to get all the linkages and put it all back together. Parts are available and it isn't too difficult a job.
To what year and model are you referring? Should it have the vacuum assist?