If it is indeed a '66, that "WW" means a 335 HP 389 (1 4-bbl), manual transmission. The date code is by the distributor and looks like a "tab" that is screwed down, where it's actually "cast in" with four digits. The first digit is the month (A=Jan, B=Feb, etc.). The next two digits are the day of that month. The last digit is the last digit of the year it was cast. An example would be "H205" would be a '66 block (next year's models start in July) cast on August 20th, 1965. That would be an "early build" for the '66 model year.
Also, count the number of expansion plugs in the side of the block. This is how we "narrow it down". A 389 has 2 plugs per side. A 400 (could have a similar casting date, ten years newer) has 3. Logical deduction gets us where we "need to be". And according to the database, that engine WOULD have "93" heads, as it IS a GTO code.
I saw a bumper sticker on Mini in `1970 that said that about Lucas, at Laguna Seca during the Monterey Grand Prix (Can Am cars WOW!!!). On the same "note", a friend, married to a British lady, drank an ice cold Coors (for me) while standing in front of a beefeater at Buckingham Palace on July the 4th, 1986, just for fun.
All joking aside, my father was stationed at Watton, 1942-45. He was a bombsight tech on B-17s and B-24s. In '95, he and Mom made it back for the 50th reunion. The town of Watton (I guess that's the nearby town) welcomed them to the point where they couldn't spend a nickel. Room, food, transportation, events, ALL "free" for American AAF vets! That's CLASS! Thank you to all Brits for the way you treated the greatest generation of Americans since The Revolution, and just maybe, EVER.