Dunlap, the Boeing Classic winner two weeks ago, also eagled the par-5 18th for a 64.
Short finished at 15-under 201 at La Tempete. He won in Las Vegas in 2005 for his lone PGA Tour title.
Brad Faxon and Esteban Toledo, the winner last year at La Vallee du Richelieu in the then-Montreal Championship, shot 71 to tie for third at 11 under. They were tied for the second-round lead.
Two-time U.S. Open champion Lee Janzen closed with a 72 to tie for 23rd at 7 under in his first Champions Tour event. He turned 50 last week.