Thank you both. From looking at the 46-48 manual, it looks like the booster brake was only used on the Crown Imperial, and not on the New Yorkers. For a 1946-48 New Yorker, would the hole in the manifold to supply vacuum be plugged, supply vacuum to something else, or not exist at all? This is a 1950 engine, but I want to make it as close to a 1946 as possible, even though I know the casting is a little different.
I have to say, the 1946-48 manual, or at least the one I have, is not very helpful compared to the manual for my '42 Plymouth.