This isn't really relevant to my original post, but I just wanted to share some success! A wideband O2 sensor with a controller that outputs a narrowband signal can work with the stock CIS computer.
I just finished installing an Innovate LC-2 controller with a Bosch LSU 4.9 sensor and the stock computer seems to be ok with the signal that it outputs on Analog Output 2.
I was able to connect the controller to my computer and check out the AFR while idling and revving in my garage. I haven't taken the car outside to monitor AFR under WOT to see how CIS behaves yet. But playing with the throttle in neutral shows me that the CIS computer corrects to 14.7 pretty damn fast.
In the place of the O2 sensor heater, I connected a 150 ohm 5W tolerant resistor, wrapped it up in black vinyl tape, and left it out in the transmission tunnel.
I do plan to later connect the more useful wideband signal to a Microsquirt ECU, but my narrowband O2 sensor was already on it's way out (threw code 17 at me the other day, cleared it never came back) and this was work that had to be done anyway. If the narrowband signal wasn't accepted by the stock computer, I would have just left the wiring from the wideband controller in place and replaced the O2 sensor with another one for the time being.