Australian Aaron Baddeley and Jace Bugg share third place at minus-6.
Buha collected four birdies on the front nine at Diamante Golf Club but it might have been his par saves that kept the round going. He drained an eight-foot par save at No. 2, then holed a pair of five-footers at 4 and 7. Buha capped off the front nine with a 10-foot par save at the ninth after he visited a greenside bunker.
Buha, a 27-year-old who has made only one of the three cuts this season, made three birdies early on his back nine but flew to the top of the leaderboard with his play down the stretch.
He ran home a four-foot birdie putt at No. 15 and added a birdie two holes later when he knocked his approach inside three feet. Buha closed out his round with a birdie at No. 18 after finding a fairway bunker off the tee.
'Last week I hit the ball well but chipped and putted like a 10-handicapper,' said Buha. 'Today I felt good as a ball striker.'
Sheehan cruised along with six birdies but started to run into trouble at No. 12. He converted a 15-foot par putt at that hole but dropped a stroke on 14 when he found the front bunker.
Sheehan righted the ship at 16 when he sank a 25-foot birdie and a birdie at the last gave Sheehan sole possession of second place.
'It was there today for the taking,' said Sheehan. 'The greens are soft enough so you could get at them. The greens were receptive. They were perfect.'
Eric Meeks, Jim Benepe, Tripp Isenhour and former Georgia Tech star Bryce Molder share fifth place at 5-under-par 67.
Full-field scores from the Buy.Com Arkansas Classic