Brian
Like many of the Beaver/Magnum chassis the up grade and changes were made mid production year and there fore there is no actual cutoff date for change over.
How ever the ABS seems to have been added in the late 1998 model year.
with abs there will be added parts, an ABS controller, modulator valves for each wheel , speed sensors and tone rings at each wheel apart from that the system should remain the same
The parts for the ABS system should be common Wabco off the shelf items ,the rotors will be the same with the addition of the tone ring cast into the back of them .
Talk to you local parts supply, give them the numbers I supplied and tell them you want the ABS version of those rotors .
Its been a while now but if I remember rightly there are only two different ABS wheel speed sensors a straight and a right angle they each pushes into a slip collar there are different length wire leads depending on application you can always use a longer cable .
Depending on how badly melted the wheel speed sensor is it should be possible to pull it blackout of the spring slip collar.
When you replace the sensor it is important that the wheel bearings are adjusted properly and then the sensor simply pushes in until it contacts the tone ring there is no need to set the air gap as the rotation of the wheel and the movement of the wheel bearings will move the sensor back to create the proper air gap
If the wheel bearing are too loose the extra movement will create too wide an air gap and the sensor reading will be intermittent or drop out.
When you order your new or remanufactured brake calipers make sure they sell you ones with steel pistons not phenolic pistons as the phenolic one tend to absorb moisture overtime and swell causing the caliper to stick and drag.
This is a link to Wabco abs part numbers
https://acrobat.adobe.com/id/urn:aaid:sc:VA6C2:26f718bd-f153-4bfc-83d0-789f7212cea4Hope this helps
Eric
