Here's an idea if you don't like the idea of drilling the manifold.
The 48 235 in the 2 ton had the vacuum supply for the brakes and rear axle supplied by a cast aluminum spacer under the carb. It has a 1/2" hose barb cast off the side. It was maybe 5/8 thick. When I went to the dual carb manifold, I made an identical one for the other carb so they would sit the same, just didn't drill the hole to mount another hose fitting.
You could mill one and use any manifold.
