Hello Dave, long time no see
IIRC the early 3.9s in the Discovery were V-belts, but the later ones were definitely serpentine belts as my 1996MY was so equipped, serpentine belt but with the old dizzy on the front, and they would have been like this up to the end of the Discovery 1 production (last model year was 1998). I have a feeling they changed about 1993 but that might be the date the 3.9 was introduced, not sure.