Very nice description and photos, I will probably link to this thread for reference when explaining the process to others. De-pinning can be a pain at first, but is not so bad once you get the hang of it.
When you reinstall the engine harness, don't forget to re-connect that plug that hides up high near the AC blower fan. I'm pretty sure the engine will not start without it; the details are fuzzy but I remember there was cursing involved.
If you need those connectors, there are a few companies that sell them (and pins too, but you need a crimper tool for them and the 'correct' one is not cheap or easy to find) if you're doing major rework or building a harness from scratch. They are the same connectors that are used in many OBD1 Honda vehicles (1993-1995 Civic, for example). Not all the companies that sell them list them as being compatible with the RX-7, but it's a pretty common connector that was also used on the Mitsubishi 3000GT, 2G Eclipse, Miata, and some older Toyotas (also the Miata and some Hondas, but those only use two or three of the four plugs).
This is a kit that will work for the '94 RX-7, but the photo on the site is generic and shows a different connector.
http://www.aemelectronics.com/plug-n...-1710-1720-781