why wouldn't you just get the leds with onboard resisters?
That said, the 95s don't have a warning indicator for bulbs. The resister is for cars that monitor the resistance in the bulbs, they have a warning light that comes on if the resistance is low, basically thinking a bulb is out. My saab does this if a brake light , turn signal or headlight goes out, but your 95 mustang does not. Plug em in and go, no worries.