http://www.westonuk.co.uk/westonuk2_114.htm

I have purchased from Weston UK and their wrap around headers (they call them swan neck headers) work very well. They make them for any engine. Send them an email if you don't see what you need. They are the only reliable source of wrap around headers that I know of. Macs won't make them because of breakage issues and Karl Mueller who custom made headers for any engine has retired.
Good Luck.