I'm working on a project that relies on 400Hz to run some old aviation instruments. What would you want for that 3-phase aviation inverter. Only really need one phase, but I could measure the impedances of the transformers and try to reverse engineer it, or just use a single phase, if it'll let me. I might also be interested in a chart recorder, mostly as a retro display item, if I can snag one for cheap. I like their look, though obviously not a lot of actual uses today.