From your question I am not sure the 39 Ford Standard you want to install the doors on is a coupe or a sedan. A friend of mine installed 1940 sedan doors on his 1940 Standard coupe, but do do so he had to cut down the top of the sedan doors a little.
Yes they will fit. The only difference is the 40 doors have wing windows and the 39 do not. The coupe door are different then the sedans.
I think the coupe is the same as the 4 door sedan, not the two door sedan. I think the two door is longer.
40 4door doors will fit on a coupe but you have to remove a little off the top back edge to close the door.