We just need to know what you plan on using everything for and why you've given it the item, nature, ability, EVs and moves it has. Any non-listed IVs will also most likely (I do this anyway) be assumed flawless, o the closest to flawless your Hidden Power type allows.
We also kinda need that sixth member.
Do not use Groudon, you do not want to play Ubers with this. It'd get mauled enough in OU as it is, with Arcanine overshadowed by Infernape, Heatran and Volcarona, Hariyama overshadowed by... Nearly everything... and Altaria.... See Hariyama....
"Whether Castform the Weather Pokemon can weather the weather is dependent on whether the weather that it's weathering is the proper weather for it to weather. Whether the opponent can weather the weather is also subject to whether the weather that it's weathering is the right weather to weather. Whether Castform can weather the opponent is once again dictated by the weather and whether that weather is the favorable weather for weathering. But most importantly, you should know whether there will be weather to weather rather than what weather they will be weathering and whether they can weather that weather."
- Smogon's Castform analysis