Crank Sensor

The 92-95 flexplate slots look similar to the ones in my 2002 3.8L. Even there, the slot design varied sometimes year-year, so tricky to decode the slots. I think it would be much easier to work off a signal from the distributor. A 70's distributor would give you 8 pulses per rev, similar to the 89 distributor. You need to convert that signal (variable reluctance) to a 5 V TTL, similar to what your 89 distributor produced. An O-scope would help you see, and you can get cheap USB ones on e-bay. I suspect a simple circuit with a few capacitors, clamps, and digital chips could convert to 5 V pulses, w/ no microprocessor needed. There may even be something for tachometers and such. Look at MSD and others. You could use either the raw VR signal, or the spikes on coil-. Tachometers use the later.

I don't know how the reference tooth was used in 1989. I doubt for spark since the distributor rotor takes care of clocking to #1 cyl (unlike later distributor-less ignitions). My guess it phased the TBI injectors to the valve opening, i.e. "sequential injection". Not essential for TBI and probably minimal value (useful only at idle even w/ MPFI). The question is if the fuel controller would still work without it. My guess is it would pulse fine from equal-spaced pulses. You don't need an engine to test it. Spin the distributor by hand and power the controller w/ 12 V. You don't even need fuel, you will hear the injectors clicking. Indeed, before you even fool w/ the 5 V circuit, you could test that. You can generate a stream of 5 V pulses from a PC audio output, using freeware on the internet. See if that satisfies your fuel controller.