I am using Nissan Z 280 turbo injectors. They are 260 or 280 cc if I remember well. If you feel they're too big you can use non turbo ones. They have several advantages:
- They are hose injectors and their shape is exactly the same as the original D-jet ones. So they fit straight, no need to fabricate fuel rails, you just reuse the D-jet ones.
- They are plenty around. I got mines by browsing on the Nissan Z forums
- they are cheap

I got mines cleaned and flow tested by "Cruzin' Performance" and he got them flowing within 1% of each other with a proper spray pattern. I sent him two sets of 6 though. Two were bad, and I have two spares.

I also have replaced the fuel pressure regulator by a vacuum actuated one. I got one from an L-jetronic Vanagon. You just fit it in place of the D-jet one, it fits straight. You have an additional port on top of it that you need to connect to the air plenum.

As you're going Megasquirt, you should also have it control the ignition. this is where you will really gain power and fuel efficiency. I went EDIS. Pictures here:
weekend Wrenching and here: weekend Wrenching