I have used Whitepost with good results.
http://www.whitepost.com/
If it is a survivor piece that you don't want repainted, make sure you tell them when you first do the work order. They did a great job on my 1973 SD455's master cylinder and it came back looking just like I took it off. (other than it was no longer leaking out the back). The turnaround time was only a week or so, too.
Here's what mine looked like before:
https://www.yenko.net/ubbthreads/ubbt...opics/539528/9
and after:
https://www.yenko.net/ubbthreads/ubbt...pics/539528/14