Yes, I believe that would be possible. The only way for Torkoal to learn Eruption is through breeding. You can find a list of parents here:
Now, it says that the Typhlosion line, Camerupt, and Smeargle are the only possible parents. However, Typhlosion is difficult to get in Gen 3 and can't learn Eruption in that Generation, and the Smeargle route is not ideal. So, it looks like your lucky Torkoal's partner is going to be Camerupt.
Numel evolves into Camerupt at level 33 and Camerupt learns Eruption at level 45 in Gen 3. Just breed together a male Camerupt with Eruption and a female Torkoal and you'll have an Eruption Torkoal!
Hope I helped! Have fun lighting up the competition!