Contributors:Well, somebody had to do it... It's not completely done, since I'd rather not download every single level segment to find out exactly what part of the level it is. But besides that, here's the basic gist of what PACs belong to which stage.
Midair Stadium
010001 : Mario vs Kirby
030001 : Primid Battle
030101 : Petey Piranha
Skyworld
040001 : Pit's Adventure Begins
040101 : Mario and Pit Team-Up
040201 : Mario and Pit Team-Up Part 2
040201a: Sub-room
Sea of Clouds
050001 : The Halberd
050102 : The Sea of Clouds
050102a: Sub-room
050103 : Off the Clouds
The Jungle
060001 : The Chase
060002 : The Chase Part 2
060002a: Sub-room
060003 : The Elevator
060004 : The Fall
060004a: Sub-room
The Plains
070001 : After the Minister!
070001a: Sub-room
070002 : The Floating Platform
The Lake
080001 : Rayquaza
080101 :
080102 :
080103 :
080103a:
080103b:
080104 :
080104a:
080104b:
080105 :
080105a:
080201 :
080301 :
The Ruined Zoo
090001 : Porky Statue
090101 : Porky
090201 :
090202 :
090203 :
090203a:
The Battlefield Fortress
100001 :
100001a:
100002 :
100101 :
100201 :
100202 :
100202a:
100203 :
100205 :
The Forest:
120001 :
120001a:
120002 :
120003 :
The Research Facility (1)
140001 :
140005 :
140101 :
140102 :
140103 :
140104 :
140105 :
140106 :
The Lake Shore
160001 :
160002 :
160101 :
160102 :
160201 :
160202 :
160301 :
160301a:
160301b:
160301c:
The Path to the Ruins
180001 :
180001a:
180002 :
180003 :
180101 : Wario fight?
The Cave
200001 :
200001a:
200002 :
200003 :
200003a:
The Ruins
220001 : Traps section
220002 : Elevator section
220002a: Sub-room
220003 : Moving platform & Door switch section
220003a: Sub-room
220101 : Charizard fight
The Wilds (1)
240001 :
240001a:
240002 :
240002a:
240002b:
240101 : Galleom?
The Ruined Hall
250001: Galleom
The Wilds (2)
260001 :
260001a:
260002 :
The Swamp
270001 :
270002 :
270002a:
270101 :
270201 :
270202 :
270202a:
200203 :
The Research Facility
280002 :
280002a:
280003 :
280101 :
280201 :
280202 :
280202a:
280203 :
280204 :
280301 : Ridley
Outside the Ancient Ruins
290001 :
290001a:
290001b:
The Glacial Peak
300001 : The entire level apparently...
The Canyon
310001 :
310002 :
310003 :
310003a:
310003b:
310303 :
320001 :
Battleship Halberd Interior
330001 :
330002 :
330002a:
330101 :
330101a:
330102 :
330103 :
330104 :
330201 : False Peach & Zelda fight?
Battleship Halberd Exterior
340001 :
340002 :
340003 :
340004 :
340005 :
Battleship Halberd Bridge
350001 : Duon
The Subspace Bomb Factory (1)
360001 :
360001a:
360001b:
360001c:
360002 :
The Subspace Bomb Factory (2)
370001 :
370001a:
370002 :
370101 : ROB's joining battle
370201 :
370202 :
370203 :
370301 : Meta Ridley
Entrance to Subspace
390001 : The entire level apparently
Subspace (1)
400001 :
400002 :
400003 :
400004 :
400005 :
400006 :
400007 :
400008 :
400009 :
400101 :
Subspace (2)
410001 :
410002 :
410003 :
The Great Maze (1)
So many to list, the gist of it is 420001 just about all the way up to 420101)
420101 : Tabuu
The Great Maze (2)
900001 : Master Hand & Crazy Hand
900101 : Master Hand (Solo)
900201 : Crazy Hand (Solo)
The Great Maze (3)
910101 : Boss Battle Rest Map
The Great Maze (4)
920001 : Petey Piranha
920101 : Rayquaza
920201 : Porky
920301 : Galleom (Wilds)
920401 : Galleom (Ruins)
920501 : Ridley
920601 : Duon
920701 : Meta Ridley
920801 : Tabuu