If you can't vent the fan to the outside stay away from LED lights.
I tried this on my last car. They were bright when just turned on and after 15 minutes they were just as dim as Halogens. Heat degrades them quit a bit. You will be disappointed unless your Halogens are really poor to start with.
Bump up your Halogen wattage or go to HID.
What bulb is in your car, I know the special Halogen HIR (High Intensity Infrared) bulbs are amazing with no conversion necessary