John,
I would either talk to Casey at Wegner or check out Clayton Machine works. His new ones are really nice. They are sand cast and then machined. They have an insert that is carbon or paintable to accent them. I have no experience with them other than I have touched and seen them in person and they look to be excellent quality. Here is a link.
http://www.claytonmachine.com/valve-covers.html
I think they would fit the spirit of your build well. Price is good too. Good Luck. Love your build!
