One advantage of reading a thread totally through from start to finish is that you don't ask questions that have already been covered. I direct you to Zoom Zoom's post on page one of this thread for your answer.
The problem is that , although the A engine was introduced in 1956, it was only used in the Plymouth until 1959. The poly engine in your 56 Dodge is the earlier version that uses the hemi as it's basis and is not related to the A engine. I have the heads and valve covers for the hemi version, but there is no single 4bbl manifold that I know of for it. The wcfb carb would work though. I will be doing a 55 and 56 Dodge some time in the future, but they will be D-500s and have hemi engines. Yes, this A engine will be available for purchase soon.
Update. The 4 bbl manifold file is done and I am in the process of scaling it to fit with one of Joseph's A.F.B.'s. The air cleaners for a duel quad setup are done. I have successfully made r.t.v. molds and resin cast those parts that will be supplied that way. The rest of the parts will be 3d printed as I can print multiple copies of them at one time and they hold detail MUCH better.
I'm moving right along on this project and plan on completion the end of May. I have successfully resin cast the block and heads. The heads have a location piece to help with getting them in the correct position. Once on the block, the intake manifold fits perfectly. The 4bbl manifold is about 2/3rds drawn.