This news article appearing in a Scranton PA paper describes the large "moving" advertisement Ford had running in Detroit For the Model T, in June 1908.
Looks like any surprise about the 20 hp Model T was out of the bag by the spring of 1908.
Among my grandfathers documentation is a letter from the Ford archives (dated 1954) stating that the model t was to be released October of 1908 as a 1909 model. Not sure if this is correct or not.
A few "Model T"s are documented sold in January through May 1908 (Ford Sales Ledgers, research by Trent Boggess) and Ford audit records show three Pre Ts sold prior to October 1, 1908. However, I think it's generally accepted that "official" Ford sales of the Model T began on October 1908.
It would be interesting to see actual detailed photos of the Pre Ts that show up as early as late 1907 at auto shows. I'd like to see the letter your grandfather had if you are able to locate a copy (more info is always good).
The display described in the news clipping must have been something to see!
Here it is, 1955 instead of 1954.
The lighted Model T on top of the Ford plant is captured in many pictures from the period. I've got one in one of my books somewhere. It would be neat if there were period movie footage showing it in action.