The winning Turnbull Stakes combination from two years ago will be reunited in this year's running of the Group One race at Flemington.

Happy Trails will be lining up for his fourth Turnbull Stakes start on Sunday with Dwayne Dunn to ride.

Dunn rode Happy Trails to win the 2013 Turnbull before partnering the gelding to a close second in that year's Cox Plate.

Glen Boss has ridden Happy Trails in his past two starts including his close fifth in the Makybe Diva Stakes (1600m).

Trainer Paul Beshara said the switch was because he wanted someone who could ride Happy Trails in both the Turnbull and Cox Plate.

Boss is the regular rider of Cox Plate favourite Kermadec.

"Dwayne Dunn will ride him in the Turnbull and the Cox Plate," Beshara said.

"Dwayne's won on him before and knows him well."

Happy Trails finished fifth in the 2012 Turnbull and was a luckless runner last year when he finished 14th after being blocked for a run in the straight.

"He was just boxed in on the rails," Beshara said of last year's Turnbull.

"He's going very well. His run in the Makybe Diva last start was very good. He was only beaten three-quarters of a length and his run was full of merit.

"His condition just ran out with about 50 metres to go."

The trainer said the eight-year-old would strip a lot fitter on Sunday as he aimed for his fourth Group One win.

"I would be very disappointed if he didn't run in the first three," Beshara said.

"He's fit and healthy and happy."

Next month's Cox Plate is Beshara's main aim with Happy Trails.

Happy Trails has contested the past three Cox Plates finishing 10th in 2012, second in 2013 and sixth last year.

Happy Trails also remains in the Melbourne Cup mix.

Sunday's Turnbull Stakes has attracted 24 nominations with Alpine Eagle favourite in an early market at $5.50 ahead of Hartnell and Royal Descent ($6.50).