Coventry City will face trips to Luton Town and Carlisle United next season.
Carlisle United after drawing 3-3 at home to Exeter on Sunday travelled to St James Park in the second League 2 Play-Off Semi-Final but went down to a Watkins goal in the tenth minute and another from Watkins in the 79th minute. John Kennedy pulled a goal back for Carlisle In the 81st minute and then O'Sullivan scored in the 90th minute.
However, a stunning goal from Stacey in stoppage time, flew in and Exeter were in the final with a 7-6 aggregate win.
The Grecians will face Blackpool in the League Two Play-Off Final at Wembley
Blackpool were 3-2 up from the first leg and went in front when former City loanee Nathan Delfounseo scored in the 22nd mnute to make it 4-2 on aggregate but Luton came back with a Mellor own goal in the 36th minute and one from Cuthbert on the stroke of half-time.
Danny Hylton scored a third in the 57th minute before Armand Gnanduillet scored in the 76th minute and in stoppage time, Blackpool scored with a Stuart Moore own goal to book their place in the final with a 3-3 draw.