the cast sections near the carbs are usually drilled to accomodate mounts for the throttle shaft linkages using a rod end, I would drill some small holes near the cylinder head face section and then link together with 3mm id rubber vacuum hose and take of from there whatever you need.

Using a single point for Brake vacuum is not as good as using two points of vacuum supply better feel with less pulsing at lower rpm.

Yes you manifold has four runners going each to an individual cylinder, I take it you are using a Redline Australian made twin side draught manifold or is it a Japanese one like Tomei?

Mikuni Solex side draughts mount solid with a phenolic (Bakelite like plastic) heat proofing spacer, Webers or dellorto Carburettors like a soft mount though the best of these were fitted standard to the datsun 2000 Roadster with the 150 HP engine option with twin 44mm Mikuni Solex sidedraught carburettors.
They may still be able to be found if you look here where they make good replacement parts.

http://www.fairladyparts.com/page28.html