Off the large port (manifold vacuum port) on the carb if you can.
Second choice would be direct to the intake as close to the carb as possible.
The reason I like right off the carb base is because it spreads that change in vacuum when the brakes are cycled over 8 cylinders instead of say cylinders 7&8 (or just the back 4 cylinders)
When you release the brakes the closest cylinders will go lean for a second or two, and I would rather spread that lean condition over 8 cylinders instead of two or four.
I realize you didn't ask me directly so, sorry if I butted in. :D
