Are you saying you want to use the same air dam with the spots for lights but instead of factory lights use aftermarket?
And as far as wiring goes, I believe the wiring for this would go down through the roof rack, down the A pillar, and then into then you'd hook it up in the interior.
Here is a link to a factory air dam with lights being sold on ebay for a good price.
FJ Cruiser Air Dam & Lights for Factory Roof Rack bar | eBay
I'm not sure if this comes with directions because i didn't read anything except the price, and I dont know if it comes with the switch that you'd add to the FJ's switch panel. But I know you can find those switches online, you just have to search for them but it should be easy.
Hopefully this helps!