I own a 67 w/ a 390 auto,power stering,power brakes thinking about adding headers for a little more h/p there is few options out there also worried about clearance issues does anybody know how far they hang down,recomend a brand or should i stay w/ the stock C70E manifolds

Try Ford Powertain Applications. They make tri-y headers with the 14-bolt flange. Very good fit and quality. They will be more exposed than iron manifolds but the FPAs are a lot better than most in that regard.