The production model immediately before the Model T was the Ford Model S, an upgraded version of the company's largest success to that point, the Model N.
The follow-up was the Ford Model A and not the Model U.
Company publicity said this was because the new car was such a departure from the old that Henry wanted to start all over again with the letter A. As it happens, the first Plymouth car (1928), built by competitor Chrysler Corporation, was named the Model U.
http://www.answers.com/topic/model-t-ford
