Hi,
I'm on the other coast so can't help you with a shop name, but from what I see in the ads of the Florida car magazines, most of the custom shops seem to be in the more populated areas. Over here, that means the Tampa/St Petersburg or Orlando area. For you it will probably be around Miami.
Are you a member of the "Cruiser of South Florida"? Here's their website...
http://www.cruisersofsouthflorida.com/HomePage1.html Someone there might be able to help you or point yo in the right direction.