Well speaking from experience using "chrome" spray paint..........DONT USE IT.
Why?
Well I added my new GTX badges to my GTX, I wanted a Black vinyl lettering for the GTX and a Chrome background to show off the GTX better. I pickup some of that "Chrome" spray paint at a local O'Rielys* (cant remember the brand name atm but its one of the popular car ones).
I spray painted the badges in the "chrome" color. And they came out okay. Not real chrome though mind you

But then I wanted to clearcoat them just incase to help keep their finish. When I applied the clearcoat, the chemical reaction between the clearcoat and the "chrome" spary paint produced a DULL gray look. The chrome faded away.
I tried to undo the mistake, but learned basically the "chrome" spray paint doesnt play well with clearcoat.
Solution? I would say sand down the black and use a good metallic finish paint instead of a "chrome" spray paint. Or IF you really wanting a Chrome finish? Have the parts "dipped" in chrome to get the real thing. But that process will most certainly cost more than the actual cost of the STB's.
Just my 2cents on that one.
You have seen several of my projects Lee when it comes to that stuff. I can speak first hand about it

Heck even Rick gave me props for my latest paint job of my Front STB and supporting braces
Here are some shots of my most recent paint job on my motor mounts and braces....
Sorry for not having any better close ups of the Front STB, but you get the picture I hope? If not I can always go out and get more or just give me a call and we can talk about it Lee.