The Pittsburgh Penguins have insisted during their extensive front office overhaul that the on-ice product doesn’t need to change much for the franchise to return to the NHL’s elite. Mike Johnston’s job is to figure out which changes to make. The Penguins hired Johnston to replace Dan Bylsma on Wednesday, charging the hockey lifer with creating the right system for stars Sidney Crosby and Evgeni Malkin to thrive. Considering the talent at his disposal, the 57-year-old Johnston likes his chances. After spending the last six years with the Portland Winterhawks of the Western Hockey League preaching an uptempo attack, Johnston welcomes the opportunity to work with one of the most explosive offenses in the NHL. “The core group is exactly where I want it,” Johnston said.