Slant 6 MPG Upgrades?

I'm soon to have my grenaded /6 back, and starting a new higher paying job so I'll have some disposable income. Being that I have my Dart to daily, and want to continue doing so, I want to maximize my actual mpg. With the modifications made to my setup, I was getting 20 mpg average, predominantly highway driving. That included removing the A/C compressor, switching to headers and aluminum intake for weight reduction, as well as an aluminum radiator. If I could have fit an electric radiator fan between the engine and the radiator, I would have liked to do it but couldn't find one thin enough.

It looks like the next big step is going to be EFI, specifically per-port fuel injection. I cannot find a straight answer on this forum or slantsix.org about this topic, and believe me I've been searching. For simplicity and to work with parts I own, I'm thinking about sending my aussiespeed intake to gill welding and having them add injector bungs and a fuel rail. I know I'll need to add pump(s) to my fuel lines, but beyond that- what parts do I need to start budgeting for and what's reliable? This is where my research has started to fall apart.
- What throttle bodies are available to replace a carburetor, but will allow me to place injectors at the end of each runner on the manifold?
- What ECU works well with a /6 and is reliable?
- Which injectors work best for the /6 and what other sensors do I need to get my hands on?
- What upgrades need to be made to my ignition? Should I switch to an electronic ignition system, if so, do any ECU's do both EFI and ignition?

Beyond that change, I want to also add on a GV overdrive system. I know it's not as low of an RPM drop as the factory overdrive units, but the 904 is the only auto trans that works with the pushbuttons, and that's a feature I want to keep. At the end of the day, lower RPMs translates to less fuel consumed, so any savings there is higher MPG which is the priority. I have no intention of racing my car, I want to reliably daily drive it for as long as I can, and I'd like to keep fuel costs lower, even if that means a higher up front cost.

Any knowledge or tips are appreciated.