I went with
3156-x18-T: 18HP-LED 16mm Wedge Base 3156 Tower Bulb for my DRLs and
3157-x18-T: 18HP-LED 16mm Wedge Base 3157 Tower Bulb for reverse lights.
On the site it clearly states not to use the 3157 for the DRLs so that's why I went with the 3156. It's $18 per bulb, but well worth it in my opinion. I went with cool white all the way around my truck, inside and out and it looks great at night.
http://www.superbrightleds.com/cgi-bin/store/index.cgi?action=DispPage&Page2Disp=%2Fspecs%2F315x-x18-T.htm
As far as LEDs for headlights...I don't know how practical that may be. Not really even sure if it can be done. Maybe someone will chime in with some info for it though.