Clint Eastwood, the "Fistful of Dollars" star, was the name Marty had to use when he was discovered by his great grandfather. Of course, when the train flew into the ravine, it was renamed "Eastwood Ravine" in honor of Marty's actions to get Biff/Buford arrested.
Now, of COURSE one can't truly argue time travel. Therefore, it can be stated that any argument that stems from the science of time travel is therefore just as false.
In any case, the real Clint Eastwood was born in 1930. According to wikipedia (http://en.wikipedia.org/wiki/Clint_Eastwood), he was born in 1930 in San Francisco, and his family lived in Oakland in the 40's when Clint finished school. Hill Valley is supposed to be in the general area of California, according to many different fansites and other threads. Wouldn't it have been logical that Clint would have heard about his namesake involved in Western Folklore, of his "counterpart" riding the train right into the ravine?
OK, another little thing that gnaws at my mind. A train ain't exactly cheap in 1885, and when Doc and Marty stole the train for the "science experiment", Doc was still stuck in Hill Valley along with Clara (who ALSO would have been a major witness in the train heist, if not an accomplice after the fact). Obviously, "Clint Eastwood" was identified, and arguably Doc Brown would have been more easily identifiable as one of the hold up men. Can anyone here come up with plausible results from this part of the trilogy, including any legal actions and investigations?
Hmm, those are some very good questions.
As to your first question, Hill Valley isn't a very big town - and the Eastwood of Eastwood Ravine probably isn't even known by first name.
As for the second question, that's a little harder. The fanon explanation that's usually given for Eastwood Ravine is that there is a legend that Clint Eastwood and Emmett Brown were trying to stop some hijackers - so the ravine was named in Clint Eastwood's honour, as he supposedly died a hero.
Here's a possible solution I thought of. Maybe Doc used the sleep-inducing alpha-rhythm generator on the train engineers - and put them somewhere, so that they would wake up and think the whole thing was a dream. They'd maybe wake up and assume that they were knocked out by the hijackers.