clean real well, use etching primer and SEM bumper paint, the stuff sticks real well and flows nice , comes in spray bombs.. try a test piece first , you might be able to just use the SEM.. it is designed to bite without the etching primer.

be ready to spend more than a few hours masking and painting the 2 colours ....

I seen a 67 grill that had just been restored last week, it is near perfect, the guy spent about 8 hours between masking and painting... He would not let me take any pictures of the car yet...not until it is all bolted back together.. it is gorgeous..frame off 67 SD ....

There was a great article in a Pontiac magazind a couple of years ago with a step by step on redoing a GTO grille. I wonder if anyone knows and has access to the article?...

I only seen the finished product, I didn't ask what he used for colours? sorry... but If I had to guess, landau black, and a satin silver ( argent ) a slight metallic but not too shiny.  the only piece that is left bright chrome is the face of the grills and surround?

I'm not near my 67 parts , just going from what I remember seeing.