If it's a headlight housing with a projector already built in, they're kind of junk. It will hook up and work on your truck, but the output leaves alot to be desired. They're no where near the quality of light output you'll get my retrofitting a set of quality projectors and HID's.
Do a search on here and you'll find a number of projector retrofit build threads.
Here is what most folks order for their Ranger: Bi-xenon Morimoto Mini Stage III Kit (D2S) - Complete Retrofit Kits from The Retrofit Source Inc
The price is SO WELL WORTH IT. Especially on back roads. Retrofitting involves baking the headlight lenses in the oven to separate the halves, clearance the hole to install the projector, aim and seal them up.
You can't use your stock housings, so order up a pair of aftermarket "euro" clear type housings like these:
1998 2000 Ranger Chrome Crystal Headlights Clear Signal Corner Lamps | eBay