PSP Version: Endgame Leveling

So besides the final dungeon, all I've got left to do is the Lifespring Grotto (twice) to fight Omega and Shinryu, and the Labyrinth of Time to fight Chronodia. I'd wager I've got to do some level grinding to have any hope of beating them. The question is, where is the best place to do so? I've gotten a bit bored of fighting Warmechs in the Sky Castle, especially since Warmech seems to have been nerfed. My party is level 54 and consists of a Knight, Red Wizard, White Wizard, and Black Wizard.

Also, what is the optimal equipment for my party? Currently I've got Ribbons and Protect Rings on everybody, my knight is equipped with a Diamond Shield while my Wizards all have Elven Cloaks, Diamond Armor on my knight, Diamond Armlet on my Red Wizard, and Ruby Armlets on my White and Black Wizards. Finally, my Knight is equipped with Ultima Weapon, my Red Wizard has Lightbringer, my White Wizard has War Hammer, and my Black Wizard has Gladius.

uh

those big mothersmurfers in the earth bonus dungeon...forget what they're called but its a rare spawn with a ghastly amount of HP. i wanna say they are giant worms but i could be wrong

The giant worms in the Earthgift Shrine are Abyss Worms. The difficulty there is that they are about as rare as Warmech, they are only slightly weaker, and Warmech is worth 8 times as much experience. Warmech probably is the most powerful random encounter in the game, it's just the rarity that makes them tedious.