Lowestoft Town will face Tonbridge Angels in the Ryman Premier Division play-off final after a 2-1 win over Suffolk rivals Bury Town.
The Trawler Boys had taken a 43rd-minute lead through Sam Nunn's own goal at Ram Meadow on Tuesday.
Chris Henderson equalised for Bury but Lubomir Guentchev sealed victory for Micky Chapman's side with a fine effort midway through the second period.
"That was different class," joint-boss Chapman told BBC Radio Suffolk.
"The boys were top drawer, we could not have asked any more of them.
"We knew it was going to be tough coming down here and it proved to be just that.
"They gave us everything we had and ran out worthy winners."
Lowestoft will travel to Longmead on Saturday to face league runners-up Tonbridge, who overcame Harrow Borough 3-2 in extra-time in their semi-final.
The winner will earn the right to play in either the Blue Square Bet North or South next season.