B intake on a RB

Supposedly the RB (raised deck) model M1 single plane had slightly better fuel distribution than the B (low deck) models, according to the old engine books.
In reality, it will bolt up just fine with spacers as you are asking, and when properly prepped they are decent manifolds.
In case the more knowledgeable pros chime in, let us know which carb flange your M1 has.