you could go with the ebay option of anzo/spyder/spec-D/etc if all you're after is appearance, but if you want any sort of serious quality light output I would strongly recommend a true retrofit. I waited about 40k miles before doing mine to my 12' halogen lights and was quite upset that i hadn't pulled the trigger on a real retrofit sooner. Check out Black Flame Customs, they're base out of CO and are currently doing some work for my second headlight project. so far great guys with fantastic communication. Be prepared to spend up to $1000, but I can promise you its worth every penny!

 

I got these

Ebay-Factory Style Projector headlights

And I upgraded the projectors to Evox-r 2.0's with 5500k HIDS and 35w ballasts for each one. Total was was probably $500. Not factory housing, but other than that I'd take these over a retrofit of the stock halogens because of cosmetic appeal

Function/output is outstanding of course

Some of my build can be found in here, as well as reviews of these headlights

OEM style Halogen Projector Headlights THREAD

 

Retrofit. End of story.