To your first question, have you tried Gardner exhaust? Are you sure Pypes doesn't have what you need? Also, the guys who are doing the repro HO exhaust manifolds are doing exhaust to. I think they are called Ram Air Enterpries, or RARE or something like that.
www.ramairrestoration.com should be their websit.
As to your question #2, I have a 65 Cat that came with a 2 bbl. Someone previously had a custom dual exhaust installed. I can't get to it right now to check where the exits are on the manifolds, BUT they are original to the car, and have never been changed.
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HONEST JERRY'S SPEED AND EQUIPMENT