https://aafords.com/c/
You might direct your question to Neil Wilson at the Model AA Truck Club at the link above.
As far as I know, Ford never supplied any fifth wheel equipment for AA trucks, but Neil will know for sure.
There is a nice era photo of a fifth wheel AA truck set up on page 79 id Jim Schild's 'AA truck supplement to Restorer's Model A shop manual.'
You might consider adapting a fifth wheel plate from a newer truck to your AA truck?
Good luck