1) Your Speedometer needs the Toyota T-Case VSS. Not related to the GM harness.
2) Your Tach needs a 12V pulse for RPM from your GM ECM. Your GM harness should have a tach output for Engine RPM. It might be 5V, which you then have to do the resistor trick. The GM ECM might be able to change the number of pulses/rev to match what the Toyota is expecting (from 4 to 3 pulses/rev).
I am not knowledgeable about this, like
@tmxmotorsports, but If your GM ECM needs a VSS, then you will need to install a VSS (and reluctor wheel) on your 4L80e.
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