Politoed @ Leftovers
Drizzle; 252 Sp.Def 252 HP 4 Def (i dont remember the nature)
-Scald -Toxic -Protect -Encore

Machamp @ Choice Scarf
No Gaurd; 252 Atk 252 Spd 4 HP; Jolly
-Dynamic Punch -Bullet Punch -Payback -Ice Punch

Raikou @ Expert Belt
Pressure; 252 Sp.Atk 252 Spd 4 HP; Modest
-Thunder -Weather Ball - Aura Sphere -Hidden Power Ice

Gastrodon @ Leftovers
Storm Drain; 252 HP 252 Sp.Atk 4 Sp.Atk; (i dont remember the nature)
-Scald -Ice Beam -Recover -Earth Power ( i need to change this moveset or this pokemon entirely)

Latios @ Choice Specs
Levitate (i think); 252 Sp.Atk 252 Speed 4 HP; Modest
-Dragon Pulse (i dont like draco meteor fo a strage reason) -Surf -Thunderbolt -that attack that does damage according to def instead of sp.defene

Gyarados @ Lum Berry
Moxie; 252 Atk 252 Spd 4 HP; Jolly
-Dragon Dance -Waterfall -Bounce -Earthquake ( im thinking about giving him outrage)

First of all, I assume your Politoed has a Bold nature, correct? If not then I recommend giving it that nature (so its otherwise low defense stat will be a bit higher). Also, you should consider switching its Sp. Def. and Defense stats. This is because Politoed already has great Sp. Def but poor Defense, and with a team like yours you shouldn’t have to worry too much about Special attacking Electric and Grass types because of Gastrodon and Latios., while Ferrothorn with Power Whip would be a problem if you didn't invest much into Physical Defense.

A Machamp with a Choice Scarf could work, although it still isn’t very fast and is outsped pretty easily in OU. If you still want to use a Fighting Type with a Scarf, try Keldeo. It would have Rain-boosted Surfs/Hydro Pumps to use which’d be extra devastating. Secret Sword would hit opponents on the Physical side, and would hit Chansey/Blissey hard.
But if you’d rather use an all-Physical Fighting-type, go with either Lucario or Toxicroak. Lucario is frail but faster and more powerful than Toxicroak (and with rain it just might survive a Fire-type Attack), while Toxicroak has more survivability with Dry Skin under Rain.

I recommend replacing Raikou with Jolteon. It’s faster, just about as powerful, and has that great Volt Absorb ability. Switch out Gyrados to Jolteon when you’re faced with an electric type, and you’ll get free HP. Keep in mind that (against smart opponents), this’ll probably only work once as they will likely use a more neutral move like Hidden Power Ice, and plus you’ll lose your Dragon Dance boosts. If you choose to keep Raikou, go with Substitute, Calm Mind, Thunder, and Hidden Power Ice with the same EVs and nature you had before.

Gastrodon with those moves and a Calm nature would work just fine. If you want something else, Tentacruel would work well on a rain team, as with the Rain Dish ability and holding Black Sludge, it could wall the crap out of opposing Keldeo and similar Pokémon. Plus Toxic Spikes and Rapid Spin support is always nice.

Latios’ set is just fine, other than that you’d be better off with Hidden Power fire instead of Thunderbolt (so Ferrothorn can’t wall you). I know it’ll have less power in the Rain, but it’s the only way to deal with those pesky Steel types. And if your Politoed gets KOed and the opponent’s Ninetales sets up Sun, it’ll be even more powerful.

Lastly, Gyrados should be OK with that set, though if you want to put Outrage in, you should get rid of Bounce. Waterfall is resisted by Water, Dragon, and Grass. Outrage isn’t resisted by any of those, and cleans away Dragons. Earthquake neutrally covers everything else. Bounce isn’t needed, really. Despite its role as Gyra’s best Flying STAB move, Pokémon like Jirachi would have no problem switching in on it, and if you still put Outrage in and took Earthquake out in order to preserve Bounce, you’d be screwed against that thing. Still, Pokémon that try to wall you like Ferrothorn (which wouldn’t want to switch out at all) would be hurt worst by Bounce, so it’s not totally a bad option. Plus it has a paralysis chance.

I hope this helped! And I’m going to test my own suggestions and get back to you on the results.