On June 11, 1969 Roberto Clemente’s grand slam caps a sixth-run 6th inning which turns a three-run Pittsburgh deficit into a like-sized surplus, an advantage the Bucs will not relinquish. “It was a frustrating contest for the Spacemen,” muses Houston Post writer Joe Heiling, “what with four errors, ineffective relief work, poor defense and some lapses in running the bases. That…