Thanks for posting that
information and 'back story'
about the Tri-Y headers,
it was very interesting and thought provoking.

Since that design is so rare,
and because they apparently worked so well,
would you consider measuring up some sizes,
and posting them?

Things like:
External/internal primary diameters.
Distance from flange to first Y
Distance from first Y to 2nd Y
Diameter of pipe from first Y to 2nd Y

Very cool story. Thanks for clearing that up.

These are cool looking pipes. I'd love to have a set myself.

Now that they have been "found" I wonder what it would take to recreate? Are these what the Dougs are based on?

Primary tubes are WAY too big for the average street motors.