I spoke to hack on the phone when looking, very nice people but said they no longer supply the kit. Focusing on newer bmws apparently. Unless there was more demand maybe?Think that may well be it
The kit has custom piping, brackets & gaskets . It's money but it makes it simple and all in one. Especially as the various online guides can be a bit ambiguous and varying. I looked extensively and getting it from the USA seemed to be the best option.
Another supplier I used for the 328 was ca automotive. They're uk, again very nice people. They do a complete kit Inc manifold but it's fairly expensive too.
Of course you could do it diy but it's not too straight forward.