1990 Bronco 8.8 Rear Question

[Ogeechee 4x4]

VSS? Is that the extra ring gear behind the ring in the rear?

Yep, that's part of the VSS. The other is a sensor that is on top of the diff and reads the teeth of that gear as it spins.

VSS is vehicle speed sensor. In my later year model, the VSS sends electronic pulses to the speedometer, there is no "cable". The truck also uses the VSS to determine the shift points for the E4OD transmission.

Also, what is the front rear, Dana 30, 35, etc.

It's a high pinion Dana 44. "Reverse cut" or whatever you want to call it.