Long time no post! I'm finishing up a production run of PrimaTech headers for the OHC six. They come in two styles, original design and a triple Weber compatible design. They are long tube equal length headers with merge collectors and fit 67-69 F-bodies and 66-67 A-bodies (haven't tried one on a 68-69 so might fit those as well). Fits power steering and power brakes.
Prices: uncoated bare original style is $560 US, uncoated Weber style is $630 US, shipping (ground) and handling averages about $90. Hi-lustre ceramic powder coating is $200. PM me if you're interested, I have enough to build a few more but time and quantity are limited!
First picture is a complete first design, second picture is a comparison of the first and second design upper sections (second/Weber compatible is the top header), and third picture is the first design upper in hi-lustre ceramic coat.