Pac Fab in So Cal can do just about anything, along with Penhall, Brenthel, Geiser and a bunch of other very capable custom fab shops. The same goes true for Arizona and Vegas where there are plenty of people with UTV's, Trophy trucks, Class One, Jeep Speed, etc.
Southern California is THE place to be for custom fab work, you have your pick of shops. How deep are your pockets?