The headlights should be drop-in replacements with no rewiring necessary. However, if your original wiring is worn or has really brittle insulation, you should think about replacing it. Most factory headlamp wiring is barely adequate for the stock lamps, and is usually undersized for any higher wattage bulbs. If you stick with the stock wattage bulb (usually 55/60 watt), you shouldn't have any problems.

95 Montero SR
3.8 MIVEC, Advance headers, 2 1/2" exhaust, Magnaflow muffler, OME shocks & rear springs, 2" body lift, 3" tank lift, 4.90s, TRE front locker, factory rear locker, Roger Brown Rock Sliderz, 315/75r16 (35") tires, Sport big brakes