Blue, are you thinking about casting your own intake manifolds? The demand for your engine would be 2.8L * 6000 RPM (I beleive is max) = 16 800 Liters of air / minute.

Forgive me for saying but It does not sound like you're a fluid engineer.

As for the air mixture, when you replace your carbs, you will have to purchase a jetting kit and determine, by trial and error what the best jetting is for you.

Too lean and you'll ping your engine to death, and too rich you'll flood/bog the engine down.

You probably know this but the way to change the jets is to disassemble the carb.

Lots of work. Good luck to you.