All LEDs are polarity sensitive. Somewhere I saw some configured for positive ground. I can't say for sure, but I'd bet HIDs, the box anyway, works with negative ground only. If the box is nonconductive it doesn't matter what polarity the ground is. Just wire negative to negative, positive to positive. I'm thinking the box supplies power to the bulb, so that shouldn't present a problem. I think it's a whole lot less confusing to just change the old gal to negative ground, then everything will plug and play.