Depends on what engine you are running. If you plan on going with the Ford 300 six, there is a Ford Motorsports cylinder head that Alan Johnson has put together, based off of the old Cleveland heads and the ports based off of the SBC canted valve head, think it might actually have a Ford part number. I have seen several of the Chevy and Ford heads cut up and furnace brazed together in the back yard. The big trick right now in Competition eliminator if you are going to run the Chevy six is to run the new DOHC motor like is in the Trailblazers or if you are going with the older cam in block motors, there are several cylinder heads that are "stock" that flow up to 420 cfm with the original port configuration. I know of a couple of people that have taken the Chevy canted valve small block head in aluminum, cut them into six individual sections, heliarced them back together to get the bore spacing right and put them on like a 250 or a 292 Chevy six. If you are really set on having a cast iron head, just PM me and I can put you in touch with several people that can help out with which heads to use, welding, and porting them.
Jeff