Can't tell yo about the first bit, I'd have to see it to figure out what you mean.
Oxegen sensors, it will run without them but think there is a fault. Change the tune select resistor for the earlier one and the ECU won't expect to see the sensor, you can also run with more advance i think, unless it's a different dizzy.
Speed transducer, later EFi had an electronic speedo driven by a sensor near, not on, the gearbox. Also connects to cruise control and EAS.
it's driven by a very short speedo cable, about a foot long and fastened to the N/S gearbox mount.
GOOD NEWS, for a few months at least RRC were built with the sensor fitted but mechanical speedo so you can buy a cable to go from the front of the sensor (it screws off) to the spedo head, thus the ECU knows how fast your are going and the old speedo still works.
If you want to make your brains hurt try wiring up an electronic speedo into your car :(mad):