Has anyone investigated what it would take to convert an l322 4.4 v8 to meet Euro 6 requirements.
There must be a way of doing it but perhaps its not economically viable

Even if someone went to the effort to get a retrofit kit certified it would be thousands, there’s no market for it.

not sure why you'd want to - My 2004 V8 petrol is ULEZ exempt everywhere in UK including London- only the congestion charge is applicable (as it is on nearly 99% of private vehicles.)