Sivir - Mid
Amumu - Jungle
Morgana - Solo Top
Galio & Urgot - Bottom

Sivir will have to be able to maximize her shield ability in mid. It's great going against characters with easy to read single target abilities where Sivir can quickly activate her shield to block the ability and regain mana. This will not only keep her in mid longer, but also give her the advantage in the 1 on 1. Playing strategically and farming should get you the upper hand to get some kills in. You might be wondering why such a strange build...very expensive, but with the teleport and her awesome ability to farm like a champion - she should have no trouble getting the items. Additionally, the ap is just enough to give her boomerang "Q" ability a very surprising amount of damage.

Morgana should have no trouble solo-top. She should be able to farm almost every single minion and harass the top character into not farming hardly any. If Sivir is having trouble mid, Sivir can go bot with Urgot, Galio can go top, and Morgana can take over. Once her and Amumu reach level 6, the ganks will be ridiculous. Amumu and Morgana both have single target stuns, Amumu's ult stuns, Morgana's ult slows and stuns -- both are in radius and ridiculous combined.

Urgot and Galio at bottom should also be quite a duo. Urgot and Galio both can kill enemies hiding in towers w/o fear of turret death. Urgot's E ability to poision giving his Q ability insane range. Following the items, you should be good on mana to maintain this harass. Galio also will be devastating with his E followed by Q.

Notice how all besides Amumu have shield abilities. All of which are extremely useful. A huge part of team battles will depend on these. Especially since both Galio and Morgana can cast on other members. Whichever member is the one being ganked can easily be saved by these shields. Additionally, 3 of these have radius ults. Galio taunts, Amumu stuns, Morgana slows and stuns. If one gets away, Urgot has no trouble bringing them back. Urgot also takes extremely reduced damage after ulting - perfect for ulting into a turret and pulling a near dead champion into the death grips of your other champions.

If it's not already obvious, the late game will depend on Sivir and Urgot to destroy turrets quickly. With Morgana, Galio, and Amumu easily controlling the opponent champions.

The main unfortunate part of this party is the fact that Morgana and Amumu get banned almost always. :/

Notes:
--The attack damage indicated on Sivir's page is lower than the actual attack damage would be, maybe it's not accounting all of Manamune's added attack -- it shows about 60 less than what actually is -- same goes for Urgot. Similarly, the AP is off for Amumu, Morgana, and Galio
Sivir will have around 300AD, with 92% crit
Urgot will have the low 400s AD (his abilities are heavily dependent on this high AD)
Morgana will have around 600 AP
Galio (because of his unique) will have around 500 AP in addition to his low 300s in MR and nearing 200 Armor.
Amumu will have 200-300 AP, but will have his W ability and sunfire cape doing continual damage.
--Morgana's move speed is not 12,707...not sure why it's showing like that.