Shhh... don't tell, but the city of University City has apparently failed to replace a couple of circa 1970s street signs.   It's remarkable that this duo of retro beauties has managed to survive amidst decades of change in the historic neighborhood north of The Loop.  A little tattered, yes, but these funky oval-shaped throwbacks have outlasted the terms of at least four U.S. presidents and the entire life span of the cassette tape.