On a tough, old-fashioned tree-lined golf course that figured to favor elite ball-strikers, it was fitting that Jason Dufner, one of the PGA Tour’s most consistent tee-to-greeners, would stand tall.  And in the end, Dufner indeed grabbed his piece of golfing immortality, claiming his first Major title by winning the PGA Championship at Oak Hill.  Pre-tournament rains softened playing conditions significantly, allowing for some truly impressive scoring over the first 36 holes of play.  On a rain-delayed Thursday, the benign conditions were most taken advantage of by Adam Scott and Jim Furyk, who shared the first round lead with five-under-par 65s.  Scott, the reigning Masters champion and a late contender at the Open Championship, did his damage early, reeling off five straight birdies at holes 4-8, then adding one more at the par-4 14th before a bogey at the 16th closed out his scoring.  Hoping to make amends for a disappointing 2012 campaign which saw him fail to hold a Sunday lead during the U.S. Open at Olympic, Furyk would also card six birdies, with only a bogey at the tough par-4 9th marring an otherwise perfect card.  Among the 35 players to break par, the strongest challenges were the 66s posted by Canadian David Hearn and the resilient Lee Westwood, another top players washed aside by Mickelson’s wake during the final round at Muirfield.  The group of players on 67 included two-time 2013 PGA Tour winner Matt Kuchar (a popular pre-tournment favorite), England’s Paul Casey, long-hitting Robert Garrigus and Australian Jason Day (seemingly now a regular on Major championship leaderboards), while those on 68 included Dufner, Open Championship runner-up Henrik Stenson and the ageless Miguel Angel Jimenez.  Tiger Woods, meanwhile, continued his mysterious 2013 pattern of coming up flat in Major play, playing 17 fairly uneventful holes in one under par before carding a double-bogey at his last hole, the 9th.  Recent Open Championship winner Phil Mickelson also posted a 71, though his far more dramatic day included a pair of double bogeys as well as five birdies from holes 9-14.  It would be on Friday that Dufner stamped his imprint on the tournament, tying the all-time Major championship scoring record (and breaking Oak Hill’s competitive mark) with a stunning 63 that vaulted him into a two-shot lead.  His round opened spectacularly when he holed his approach to eagle the par-4 2nd, but then things became more methodical as he ticked off five subsequent birdies before leaving a 12-foot putt short at the final green that would have made him the sole man ever to shoot a Major championship 62 rather then the 24th to shoot 63.  As it was, he tied the tournament record for low 36-hole score, but his lead was hardly commanding.  Indeed, the trio of players most closely pursuing him included Scott and Furyk (who both shot 68) as well as Kuchar, whose round of 66 included five birdies, plus a bogey at the demanding par-4 18th.  With scoring conditions again benign, there was nearly another 63 recorded as 2012 U.S. Open champion Webb Simpson moved into the mix via a seven-birdie 64 that included an untimely bogey at the par-4 7th, his 16th hole of the day.  Though commonly viewed as “Moving Day,” Saturday actually produced only limited shifts atop the leaderboard, with Dufner fighting off the standard post-low round malaise to post a 71 – just enough to let Furyk slip into the lead by one.  Conditions were dryer and tougher, and scoring climbed accordingly, with Furyk’s 68 (which included a resilient recovery from two early bogeys) being the lowest round recorded among those who began the weekend in close proximity to the lead.  Several outliers posted lower numbers to move into the mix, however, including Jonas Blixt (a 66 to climb to fourth place, three strokes back) and former world number one Rory McIlroy, whose 67 moved him to the edge of contention, six shots in arrears.  Stenson, for his part, posted a solid 69 to trail by two, while both Adam Scott (a disappointing 72) and Steve Stricker (70) stood tied for fifth, four strokes off the pace.  As is often the Major championship case, Sunday evolved largely into a battle of who could hit the most fairways and greens – and there, perhaps predictably, Dufner shined.  Cognizant of having lost a late four-shot shot lead (and the ensuing playoff to Keegan Bradley) at the 2011 PGA, Dufner was determined to put his best foot forward and wasted little time in doing so, logging birdies at the 4th, 5th and 8th to retake the lead – with his cushion extending to two when Furyk bogeyed the difficult 9th.  Thereafter, Dufner did his best impersonation of Jack Nicklaus, methodically posting back nine pars before giving himself a bit of wiggle room by pitching to within two feet to card one last birdie at the 16th.  Furyk matched that birdie to stay within two but could do no better than bogeys at the brutal 17th and 18th, a failure to mount a final charge that rendered Dufner’s own pair of closing bogeys irrelevant.  The red-hot Stenson, trying to become the first Swede to win a men's Major, crept within two shots on the 13th hole and appeared ready to charge as he faced the driveable par-4 14th.  But his tee ball found a divot, he buried his wedge approach in a fronting bunker, then blasted out poorly to make bogey; he would claim solo third, three behind Dufner.