A David Mooney injury time winner was enough to see Orient progress in to the fourth round of the FA Trophy as the visitors ran out 3-4 winners.
After going in to half time a goal to the good, the O's streched their lead to three before Dover Athletic pulled it back to 3-3 but for a David Mooney winner in the dying minutes.
Head Coach Justin Edinburgh made three changes to the XI that started in the mid-week win away against FC Halifax Town.
Joe Widdowson slotted back in to left back after he served his suspension, Lamar Reynolds made his first start since the last FA Trophy tie at Bognor Regis while Matt Harrold started in attack in place of the ineligible Dan Holman.
New signing James Brophy last appeared for the O’s in November at the Matchroom Stadium and started this afternoon’s fixture on the bench after signing permanently from Swindon Town on deadline day.
The two sides previously met at the Matchroom Stadium in November when a Craig Clay equaliser cancelled out Nortei Nortey’s first half opener.
The O’s got the game at The Crabble underway with the first chance falling Dover’s way, Gallifuoco sent a header towards goal which almost looped over Dean Brill and in to the net.
The hosts continued to put pressure on the O’s early on when Anthony Jeffrey powered an effort towards goal but for Brill to smartly save behind for a corner kick.
From the corner, Connor Essam found himself free in the centre of the box and volleyed a shot inches wide of the post.
It was a quick start from Dover and the O’s looked get the ball down and play when Ebou Adams won possession back in midfield before finding Matt Harrold through on goal who forced a very good save from Mitch Walker in the Dover net.
Another nice chance came about for the O’s when Lamar Reynold’s found Macauley Bonne out wide whose cross to Harrold forced Walker to come and collect the ball.
Reynolds was heavily involved again when the winger forced another great save from Walker after the midfielder received the ball of the edge of the box, cut in and rifled a shot towards goal.
From the resulting corner a scramble inside the six-yard box saw Josh Coulson, Harrold and Bonne go close but for a combination of good defending and goal-keeping from Dover Athletic.
An end to end first half hour saw Brill dive down to his right to gather a powerful headed attempt from Gallifuoco.
George Elokobi opened the scores for Leyton Orient when the central defender headed home from a Jobi McAnuff corner.
Yet another smart save from O’s ‘keeper Brill who got down low to tip Nortei Nortey’s long range effort passed the post for a corner.
On the stroke of half-time Harrold had his shot cleared off the line by Josh Passley after the forward done well to hold off his man and get the shot on target which called an action packed first half to an end.
The second-half began as the first ended, Bird headed straight at Brill after Mitch Pinnock’s hanging cross found the forward.
Seconds later, Bonne doubled the lead for Orient when the striker picked up the ball 30-yards from goal and placed a beautifully weighted effort in to the top corner leaving Walker stranded.
Four minutes later, Harrold made it three when George Elokobi headed the ball to the feet of the striker who managed to poke it passed Walker to give the O’s some daylight.
But Dover managed to pull one back within minutes, through Bird who poked home a shot from Pinnock that was going wide of the far post before the deflection took it goal-wards.
Jeffrey fired a rocket in to the side-netting from 20-yards out, which fooled the fans in to thinking it went the other side of the post.
After a quieter spell in the game Bonne had the chance to wrap up the tie when Harrold’s through ball set the striker through on goal but for an excellent save from Walker.
Dover clinched another with nine minutes to go when Coulson’s clearance could only go as far as Pinnock who paced the ball over Brill to make it 2-3.
Seconds after the restart the hosts levelled the scores through Bird who tapped home after Kadell Daniel’s initial shot was saved.
With four minutes added on James Brophy played in David Mooney who took a touch and smartly lifted the ball over the 'keeper for an excellent finish to put the O's back ahead and in to the fourth round of the FA Trophy.
DOVER: Walker, Passley, Ilesanmi, Gallifuoco, Parry, Essam, Brundle (C), Pinnock, Bird (Alabi 86), Nortey (Bellamy 61), Jeffrey (Daniel 73)
SUBS: Lewington, Okosieme,
GOALS: Bird (57), Pinnock (81), Bird (83)
ORIENT: Brill, Caprice, Coulson, Elokobi, Widdowson, Adams, Clay McAnuff (C), Reynolds (Brophy 67), Harrold (Mooney 82), Bonne
SUBS: Sargeant, Koroma, Happe
GOALS: Elokobi (34), Bonne (48), Harrold (53) Mooney (90)
REFEREE: David Rock