I had them on my 996 C4 and I don't recommend doing it. I got them cheap so I figured I'd give it a shot and there's a couple of problems:
1. No matter how good the paint, they are in a bad location for catching water and road debris and the paint will probably peel.
2. They are hard to attach firmly. The standard method is double stick tape. They'll come off after not very long that way. You could use a more permanent solution but then you'd mess up your headlight lenses.

Just stick with the stock headlights and modify something else.

 

They come with glue ( two compunds) and they stick really good. No problem at all. I also did clear bra on it and non paint chipped. They are fine. Of course is something they you have to like.
I was not happy with look of the light.
So used to my last 1991 964 Turbo.