This may open up a can of worms, but I need to know the right answer

I have read previous posts from members as to which number is correct. The one labeled "ch nr" on the square plate passenger side fire wall or the number stamped into the firewall drivers side under the heater (in my case both numbers are the same) or the metal plate painted over on the passenger side front spar
I personally have emailed Volvo in Sweden to ask the question "is my engine # ****** and VIN # ****** matching, the answer was yes. The number that I used was the six digit one on the squarish plate held on with 4 screws on the passsenger side firewall. Together with a pic of the plate and this letter I was able to convince the DMV(they claimed an 8 digit number is what is required) to reregister my car (I lost my ownership and had to prove my case).

The school of opinion seems to be divided as to wether this is the correct one to use. I have been unable to locate the Round Fender Registry to get a definative answer. Have they moved or closed? Does anyone have a current web or e email address. Your opinions are welcome
Steve