Almost a 6 month bump, but I have a mod unrelated to the engine replacement now
Got the head unit upgrade completed in the Miata. Axxera XDMA7200 for $120. Sure it's cheap, sure it's just linked into the factory Bose speakers (with an in-line pre-amp to avoid frying them), but my first audio project and everything worked fantastically. Full time hands free, USB, Aux-in, or Bluetooth music, and that's all I was asking for. The no-antiskip CD drive in the OEM HU was worthless, and the cassette deck somewhat more so. I'm not an audiophile, and spending more money on audio is wasted on me anyway (plus I'd rather avoid adding weight, removing the OEM HU and cassette deck is a weight reduction at least). No more need for more than the 1 12v plug either. Constant phone charging source from the HU.
While I was at it, I tapped into the constant 12v power and ignition switched power and added 3 feet of leads to each, capped them off, coiled them up, and tucked them up under the dash. I figure I may need them at some point, and this will make it easy to access later.
Still need to add a manual switch to the power antenna. Will probably just cut the line completely at first, and worry about a manual switch later. Any power at all to the HU extends the antenna, and for some reason having that antenna extended irritates me. No way of avoiding it, since it uses the same power wire as the pre-amp, just have to add an in-line switch between the junction and the antenna. Doubt I will ever actually extend it though, since even retracted it gives me enough reception typically. And I won't be using the radio much any more, if at all.