I'm thinking about moving to fuel injection, after reading the datsun1200 entry on how comparatively easy it is. Since I don't have an EFI manifold I'd have to build one, which is okay, but I'm wondering: for a non-racing daily driver, any guesses as to the plenum interior volume? I've read a lot of estimates and calculations, but I suspect "whatever Datsun did" is probably the right answer.
Thoughts?

ZERO plenum volume for best HP

That is sweet. What ITB's are those?
I'm partly interested in a plenum because I may boost the engine at some point, at which point I know volume doesn't matter so much because the pressure makes up for it. But that's a huge project so getting it driving with FI first seems like a good idea.

Those are 35mm motorcycle throttle bodies. When you have four ITBs u dont need a plenum

Where a plenum really helps is when you have only one throttle feeding four cylinders. Like this EFI manifold (127 hp dyno'd)

Okay, that's really cool too. What ITB is that? It looks like all it needed was holes redrilled to make it fit onto a stock intake manifold? That would make my life a lot easier.

So how do people manage fuel flow through a single injector? Make it four times as large, or have it operate at four times the duty cycle?

If you have four injectors, u need to make them each four time smaller than a single injector. The one in the photo is an inexpensive 800cc injector

The throttle body on the stock intake is a 40mm Hyundai Accent 1995-1999 part. See $1200 EFI Turbo A12 (the EFI doesn't require the turbo, and it all fits on a stock A12 -- stock block and stock head)