Welcome back! I for one would love to hear more about specific details on the integration. I don't know the Miata engine auxiliaries well. Did you retain all the stock injection and computer? How does all that get mated to the Alpine? It sounds like the Miata integration was much simpler.
Jay,
I would actually venture to say that the wiring was the hardest part of the entire conversion. I had a donor car that I stripped the harness out of to start. After that, I labeled everything that I wanted to remove and stripped those wires out of the car... Headlights, Turn Signals, Airbags, ABS, Power Steering sensors, etc. I think i removed 15lbs of wire all said and done!
The factory computer was retained and I hid the entire computer under a the 'False Floor' in the passenger side foot-well. This is actually the same place the computer is on a Miata. The similarities in the two cars is really uncanny!
Integrating the remaining engine harness into the alpine was really pretty easy after that. I hooked up the main power from the battery to the starter where it was on the Miata. I used the same wires from the ignition switch to the back of the Alpine Switch (It HAD to look right with the hood down!) That was really it, The alpine distributes the power to the rest of the car via one or two wires on the fuse block, so hook those up to power and, Viola, running car!