CREATE TABLE table_74818 ("Week" FLOAT, "Date" CLOB, "Kickoff  ( ET ) " CLOB, "Opponent" CLOB, "Result" CLOB, "Record" CLOB, "Game site" CLOB, "NFL Recap" CLOB)

Which Opponent has a Game site of heinz field, and a Record of 3 1?
SELECT "Opponent" FROM table_74818 WHERE "Game site" = 'heinz field' AND "Record" = '3–1'
SELECT "Opponent" FROM "table_74818" WHERE "Game site" = 'heinz field' AND "Record" = '3–1'