Jason,
I hope this doesn't violate the advertising guidelines, but try Toefco Engineering just to the north of South Bend in Niles, Michigan.
P.M. me if you need their info.
I have no connection in any way to the company, but they have done powder coating in the past for me, including a set of Z 28 wheels.
They do an excellent job.
Jon
http://www.geocities.com/jon72vega/my_page.html