I think people are getting confused here between a Mass Manifold and a Mass Style Manifold and anything that looks like a big bunch of bananas these days is getting called a 'Mass Manifold'.
But that style of big pipes with the number one sweeping right over the top was done by a few people including Specialised Exhausts... in fact we do one, which is on Webbys Anglia.
But if you have the 4 separate primary's you need to pop over and see someone like Simpson and get them to make you a collector that the 4 pipes will slot into.
They were like that ont he hotrods (Anglias, Escorts, Starlets etc) to stop them cracking at high revs, which was a problem Gordon Streeter had when he fitted one of ours to his race car, but now its all mounted up with support and its been re-welded its ok...