This is the registration page - you need V5c and the some kind of proof - a homolgation letter is the listed, I've no idea if you'd be able to get in touch with a human to find out if there's a process for where that's not available....
Mine was a late 90's car (non turbo - is it true that turbo's are generally cleaner?) and the NOX on the homologation letter was well within the limit. Love to hear if you managed to do it!
This is the registration page - you need V5c and the some kind of proof - a homolgation letter is the listed, I've no idea if you'd be able to get in touch with a human to find out if there's a process for where that's not available....
https://tfl.gov.uk/modes/driving/compliance-registration/before-you-start
Mine was a late 90's car (non turbo - is it true that turbo's are generally cleaner?) and the NOX on the homologation letter was well within the limit. Love to hear if you managed to do it!