For what it's worth, I have twin H/W's on my Cadillac 261 with a little cam in a '50 3100 and I ran the vacuum to the dist from the front carb and it seems to work fine. The engine pulls hard from idle to 5K. It gets driven every day (mostly) and raced on weekends. Down the road it gets 20-22mpg with 4.11 gears and a 5 speed.

1964 Chevrolet C-20 Fleetside, Otis
1950 Chevy 1/2-Ton, Kirby
1950 Chevy 1/2-Ton Shortbed, Walter