Terrakion would have a hard time in OU as a stealth rock user, since it would lose a lot of momentum unless you get a good switch in. You generally want to use it as a sweeper and then you'd rather have one extra attacking move for coverage. It's not that good defensively either so setting up rocks can be difficult. Therefore I recommend Heatran instead.
Heatran is very versatile. You could give it a Z-crystal. Leftovers or even as you said Air Balloon or Shuca Berry. However I'd recommend not worrying too much about the ground weakness, it is better to switch out in situations where Heatran is threatened by ground types.
Its ability Flash Fire is good if you can predict your opponent, even if you can't it will put pressure on them. It synergizes well with Pokemon that are weak to fire such as Mega Scizor.
Depending on your team you could either go bulky with 252 HP or offense with 252 SpA EVs. The rest would be maxed out speed and the remaining 4 in HP/SpA depending on what you maxed out. Modest or timid nature.
When it comes to moves you want Stealth Rocks (obviously) + (Toxic/Will-o-Wisp + 2 attacking moves) or Stealth Rocks + 3 attacking moves. The most popular moves are Flash Cannon, Lava Plume/Magma Storm, Earth Power, but for coverage you could even go with Dark Pulse, Dragon Pulse or whatever Hidden Power you would want.
If you just want the standard Heatran you can use this one I took from Smogon.
Heatran @ Steelium Z
Ability: Flash Fire
EVs: 252 SpA / 4 SpD / 252 Spe
Modest Nature
- Flash Cannon
- Lava Plume
- Earth Power
- Stealth Rock
