where to train at lvl 68

[The Legendary Joe]

There's also Byalan 4 with Marcs and Swordfish, and if you have healing items or feeling gutsy, could try floor 5 for Strouf and Merman and the occaisional Deviace (Just watch out for that cursed Eralia if you do go down there, and water/wind armor/wings are recomended for when strouf/swordfish hit you with magic)
they give much better zeny.

If you have hydra carded weapons, you could try going Rachel sanctuary, but be careful, you're still pretty low level for this place, but it is Possible to work here. And you'd need to do a quest to gain access.