Ford 8.8's in the trucks always came with ABS sensors on the top of the differential.
All the broncos that have RABS, and 4WABS use that sensor. On the 1992+ trucks, that sensor is used to drive the speedo, which in turn feeds the EEC with information.
Pre-1992, the VSS information, NOT ABS information was fed from the transfer case via a speedo cable. I haven't seen too much information on it, but from what I've gathered from this forum, somewhere in line, there is an encoder that the speedo cable goes through, and then up to the speedometer. In that encoder is where the VSS information is generated for the EEC/E4OD control, NOT the ABS information.
The Sterling 10.25, and SOME D60's that were found in the E-series vans came with ABS sensors on the differentials, NOT the D70.