hesham is right, the "Pa.323 AC3" is mentioned by Gérard Hartmann in his article "Les réalisations de la SNCASE"
(via
http://www.hydroretro.net/etudegh/ ) as one of the contenders for a twin engined attack aircraft.
But the Pa.321 AC3 isn't mentioned there, which definitely should have been, as it was a well-proven entry for
that contest !
I found an entry in one of the lists, compiled and edited by Ferdinand C.W. Käsman, in collaboration with Roland
Payen himself:
View attachment 641468
It should be noted, that he tagged it with a question mark, to my opinion, clearly indicating, that he wasn't sure about it
and maybe Monsieur Payen not, too.
The article on hydroretro was published in 2005, the meeting between Käsman and Payen took place in 1993, so long before
and from what I read, Monsieur Payen's memories already had faded a bit, fully understandable, regarding his age then:
View attachment 641470
(The last sentence of that note by Mr. Käsman says " .. unfortunately, Monsieur Payen himself quite often isn't sure anymore
<about those designations>" )
If Monsieur Hartmann had knowledge of this list, is unknown to me, but if not, his table of contenders was incomplete,
omitting a proven entry, replacing it with an unproven one. Not very probable, I think.
Judging the available sources, and the comments by Mr. Käsman, I rather think, the "Pa.323 AC3" is a result of a wrong memory
by Roland Payen himself.