Ganguly top-scored with 144 as the tourists piled on 362 for six in reply to Australia's first innings of 323.
"It is a huge confidence boost that we've started well," Ganguly said. "We know we've started to play well overseas (in the past year).
"The bowlers were really disappointed after the first day but we came back and bowled well after that. We're very happy with the position we're in after the fourth day.
"Although it's a great start here, it's a challenge for us to do that in the next three Test matches."
India's record away from home is very poor, having won just six of their last 68 matches on foreign soil. They have won only three Tests in Australia, but staged a remarkable turnaround to beat Australia 2-1 at home two years ago.
"I'm very happy to get a hundred, especially in Australia," added Ganguly, after scoring his 11th Test century but first against Australia. "All Test centuries are important, but some are a little bit special and this is a special one.
"We're playing the best team in the world and when I walked out we were 62 for three so, from that point of view, scoring a Test hundred in Australia is good.
GOOD SIGN
"It's also very important for the team. It's a very good sign for the team that we can score runs when Sachin doesn't."
Tendulkar was controversially given out for a duck to leave India on 62 for three, with television replays suggesting the ball would have passed well above the stumps.
Australia fast bowler Jason Gillespie admitted he was surprised when West Indies umpire Steve Bucknor eventually gave Tendulkar out leg before wicket.
"I was surprised because I appealed for so long and didn't get a response so I assumed it was going to be given not out. So it was a pleasant surprise," he said.
Australia's bowling attack had been weakened by the absence of Glenn McGrath, Shane Warne and Brett Lee but Gillespie led the charge with three for 45 off 25 overs.
"I didn't feel any undue pressure, we've still got a very good bowling attack," Gillespie said.
"The Indians played pretty well, I thought. They left a lot of balls and just put the bad ones away.
"We know that India have got a lot of good players who have got great records and have played pretty good in the past so we'll just stick to our game plan."
