Incumbent Test opener Marcus Harris is finding form ahead of the men's Ashes after starting this season with a Sheffield Shield century for Victoria against New South Wales.

Harris (137) and Peter Handscomb (115) boosted their cases for Ashes selection on a windswept third day of Victoria's clash with New South Wales in Sydney.

The venue-record stand of 261 runs at Drummoyne Oval allowed Victoria captain Handscomb to declare his side's second innings at 3-290, with the Blues to resume at 1-33 on Saturday after being set 339 for victory.

Will Pucovski looms as the frontrunner to open, alongside David Warner, when the Ashes start in Brisbane on December 8, provided he is able to recover from a 10th concussion.

Usman Khawaja already has two centuries from four Sheffield Shield knocks this season, plus the experience from playing 44 Tests.

But Harris and Handscomb — forced to wait seven weeks to enter the race for spots in Australia's Test squad because of border closures — have underlined why they should be in the mix.

Harris spent seven-and-a-half hours at the crease, completing his 19th first-class ton after a productive winter stint with Leicestershire that featured 655 red-ball runs at an average of 54.6.

He said he'd learned not to worry about Test selection, nor the form of rivals such as Khawaja.

"If you look too far ahead with that stuff, you can get yourself into a bit of trouble," Harris said.

"It was hard work [today], I'm not sure I've had to bat that long for a hundred since probably my first hundred."

New South Wales fast bowler Trent Copeland said he had noticed improvement in Harris's game since the Victorian made his Test debut in 2018.

"Having bowled to him a lot over the years, he used to be really off-side dominant," said Copeland, who played three Tests for Australia.

"This was probably to his detriment when he first started playing Test cricket.

"He's very much scoring 360 degrees now. He looks a complete player. He had a big, big off-season in the UK.

"He looks primed if there's a position at the top of the order for Australia."

Labuschagne among the runs

Test star Marnus Labuschagne cashed in again with the bat for Queensland, but Tasmania has given itself hope of an unlikely victory in an intriguing Sheffield Shield clash in Townsville.

Tasmania collapsed to be all out for 182 early on day three, having resumed on 4-150.

Queensland — having declared at 6-487 in its first innings — raced to 1-132 in its second dig, before captain Usman Khawaja declared once again.

Labuschagne finished unbeaten on 60, backing up the 136 he scored in Queensland's first innings.

Former Test opener Joe Burns — at 46 not out — was also among the runs.

Queensland's declaration left Tasmania with a daunting 438-run victory target, but the visitors dug deep to reach 1-127 at stumps.

Tasmania needs another 311 runs on the final day to win.

Caleb Jewell is unbeaten on 65, but fellow opener Tim Ward (54) fell shortly before stumps.

AAP/ABC