Credit Ford with a classy move yesterday when it strategically left the blinds open in certain offices at its World Headquarters in Dearborn. The effect was a building-sized birthday card congratulating its cross-town competitor, General Motors, on making it 100 years in the automotive business. Ford celebrated its centennial a few years back, so knows how much fun the big 1-0-0 can be. And though they're technically competitors in this grueling business, both Ford and GM often find themselves in the same boat when it comes to battling imports for market share, appealing to the federal government for loans and generally doing their best not to make Detroit an embarrassment. Did you know that GM almost bought Ford back in the day? The man responsible for making GM what it is today, Billy Durant, made Henry Ford an offer of $8 million to buy his six-year-old car company on October 5, 1909... and Ford accepted. Unfortunately, Ford demanded $2 million up front, preferably in gold, and Durant couldn't get the loan approved by New York banks. The two automakers' paths verged from there, but obviously never completely separated.