Emmanuel and I met up today, and he will (probably) post some photos of my tube headers for your edification. He had a similar set-up for his car, but now he thinks he may have a better solution (O JOY) ! We looked at "427 shorty" cast Iron headers (very rare AND expensive), but if he's correct, it would look "stock" and "period correct" for those who are fussed about such things.
My car runs great, and the heat issue is mostly a thing of the past, partly due to these ceramic-coated headers. i'm satisfied... for now...
Paul - To answer a question you posed a long time ago on 'Frua restoration part 2' - yes; I do now have a subtile (and removeable) front spoiler. I followed Emmanuel's lead, it's virtually invisible and works very well.