I think your going to be hard pushed to convince TfL even if it was Euro 4, they seem to have convonced them selves that pre 2006 is the cut off point anyway.
He says, with interest, as with 2 x 2003 3.2 Manual Specials which are potentaily Euro 4 but dont show on the list?.
TfL: "If you believe that your vehicle meets the Euro 4 / IV standard (Euro 3 if you are a motorised tricycle or quadricycle), you will need to register it with us providing evidence of its emissions. "
https://tfl.gov.uk/modes/driving/emissions-surcharge/registration-47575 Then you will need to Upload documents:
"We need to see evidence showing the vehicles qualifies for registration do that you don’t have to pay the T-Charge. We need to see evidence showing the vehicles qualifies for registration do that you don’t have to pay the T-Charge. Please upload images of
The vehicle registration document (V5C or country equivalent)
AND
A signed letter from the vehicle manufacturers homologation department showing the vehicle registration mark (VRM), the Vehicle Identification Number (VIN) and the Euro standard the vehicle was manufactured to.
"