To know for sure which differential is in *your* specific 1997 Dodge Ram 1500, you'll need to check:
* The sticker on the driver's side doorjamb: This usually lists the axle ratio, which can be a clue.
* The differential itself: Look under the truck for the differential housing. The casting might have markings indicating the manufacturer and model.
* Your vehicle's documentation: If you have the original owner's manual or build sheet, it might specify the differential type.
Without looking at the truck itself, it's impossible to definitively say which differential it has.