The San Francisco 49ers overturned a 17-point half-time deficit to book a Super Bowl clash with the defending champions, the Kansas City Chiefs.The 49ers scored 27 unanswered points as they beat the Detroit Lions 34-31 in the NFC Championship game to book a trip to Las Vegas.It is their second Super Bowl appearance in five seasons having lost to the Chiefs four years ago.Victory – and the chance to win a Super Bowl for the first time in 29 years – looked a long way off when Jameson Williams ended the opening drive with a 42-yard touchdown run and David Montgomery went in from close range to give the Lions a 14-0 lead in the first quarter.Christian McCaffrey cut the gap from two yards early in the second quarter, but Jahmyr Gibbs ran in from 15 yards and Michael Badgley added a field goal to stretch the Lions' cushion.The game swung after the interval as the 49ers scored 17 points in eight minutes.Jake Moody landed a field goal before Brandon Aiyuk caught a six-yard touchdown pass from Brock Purdy – after the pair had connected on a 51-yard throw via the face mask of the Lions’ Kindle Vildor – and McCaffrey went in again to level the scores.The 49ers are going to #SBLVIII! #FTTB pic.twitter.com/iCz0Fo5OSQMoody kicked them ahead for the first time before Elijah Mitchell’s three-yard run stretched the advantage, Williams’ late score leaving the Lions too little time to create another chance and ruing two failed fourth down attempts in kickable range."We played as bad of a first half as we could," coach Kyle Shanahan told Fox. "It’s been a long year to get to this point and we got it done today."It was hard at the beginning, but the character we have in our team, the type of guys we have, we can’t wait to get to Vegas, man."