Terry Lawlor made it two wins from two starts in the Heritage Touring Cars on a soaked Saturday at the Bathurst Motor Festival.
The New South Welshman made the most of his pole position to lead home Bryan Sala's Ford Sierra RS500 in both six lap heats.
Sala chased gallantly but could not find a way by the GIO GT-R, losing out by just 0.4s in Race 2,
Mark Eddy's HR31 Skyline completed the top three on both occasions, while Duncan MacKeller (Sierra), Chris Stillwell (Sierra) and Gary Colins (Commodore VL) shared the remainder of the top six places.
Muston ran as low as 10th in the early stages before making an early pitstop, after which he comfortably proved the fastest man on track and eventually emerged ahead after the cycle was completed.
Iain Pretty/Scott Fleming (Roaring Forties GT40), Greg Taylor/Barton Mawer (Audi) and Mark Griffith (Audi) completed the top six, while Carrera Cup star Nick McBride managed seventh in an aging Porsche GT3 Cup.
The pole-sitting Andrew MacPherson/Brad Shiels Porsche was out on the very first lap, with MacPherson crashing at The Cutting.
The Production Touring Car 1 Hour saw HSV drivers Daniel Flanagan and Keven Herben score a one-two finish, taking the flag just 0.8s apart.
Dylan Thomas, who had led the early stages of the race before losing out in the pitstops, took finished in his Mitsubishi ahead of his father David (Mitsubishi) and Matt Holt (HSV).
Another HSV driver, Zach Loscialpo, had earlier escaped injury when he ran off and rolled six times at The Chase on the opening lap.
The day's other races were taken out by Brad Tilley (Group N), Shawn Jamieson (NSW Road Racing) and Travis Lindorff (Saloon Cars).
Another full day of track action is scheduled for Mount Panorama tomorrow.