Australia fly-half Larkham, who will move to Murrayfield after the World Cup, believes the Wallabies would receive a huge boost by upsetting the All Blacks at the MCG.
"A win would be very important for our psychology," he said.
"We certainly want to get some confidence out of these matches with pretty much the team and the same combinations we are going to take into the World Cup.
"We want to get a little bit of confidence out of that and I think the best way to do that is to beat the sides that you come up against."
The 33-year-old acknowledges, however, that New Zealand will be the team to beat at the World Cup.
Larkham claims the All Blacks can walk away with the title in France, but warned that their glittering Test form will count for nothing if they fail to turn it on when the quadrennial tournament gets under way on September 7.
"I think on paper they (New Zealand) certainly have the team to do it," Larkham said.
"It is just a matter of preparing for each game and being physically and mentally right for each game.
"In a World Cup it comes down to who plays best on the day, it doesn't necessarily matter about your form previously."
Despite dominating rugby over the past 10 years, New Zealand have not managed to win the World Cup since 1987, and have been knocked out of the competition at the semi-final stage at their last two appearances.
Larkham added: "We saw in the 1999 World Cup, France had a blinder against them and came away with the victory and that was the end of their campaign, and in 2003 we played exceptionally well [to win the semi-final between the teams].
"I think you look at those sides that were in the 1999 and 2003 World Cup and on paper they were some of the best sides around, even to date, and I think it is the same this year with the New Zealand side - fantastic on paper."