pokemon0078, I'd put Specially Defensive over Scarf, but it should be the third set mentioned in terms of viability.
Scizor is only a free switch if it's choiced to a move that's not Superpower, otherwise it's dangerous to Heatran.
In offensive set I'd put Stealth Rock first on the fourth moveslot and maybe Toxic for pesky Volcarona, who otherwise can Quiver Dance and Roost in your face even if you use Earth Power:
move 4: Stealth Rock / Toxic / Taunt
Flame Charge is too situational and you will be switching Heatran too much in this metagame to be useful at all. I'd rather add Protect as a fourth option or mention both in AC. Mention that Offensive's Earth Power does not OHKO Specially Defensive Heatran, but it will OHKO in the reverse if there's no air balloon:
252+ SpA Heatran Earth Power vs. 248 HP / 252+ SpD Heatran: 300-356 (77.92 - 92.46%) -- guaranteed 2HKO
0 SpA Heatran Earth Power vs. 0 HP / 4 SpD Heatran: 308-364 (95.35 - 112.69%) -- 68.75% chance to OHKO (guaranteed after Stealth Rock).
I'd mention that Heatran should always wear Earth Power in its moveset, it's too good and necessary to deal with other Heatrans and many switch-ins like Terrakion or even Volcarona. Mention that, however, you'll need to gain the speed tie. Offensive Heatran VS Offensive Heatran will be up who chose the better EV spread or who wins the speed tie.