Dungeon 1 vs Dungeon 2 Armor Sets
Lightforge Bracers can be purchased from the Auction House.
Soulforge Bracers are obtained by upgrading the Lighforge Bracers by completing the An Earnest Proposition quest given by Deliana in Ironforge.
I was able to start the upgrade quest at level 58.
Lightforge Belt can be purchased from the Auction House.
Lightforge Gauntlets can be purchased from the Auction House.
To upgrade the Lightforge Belt and Lightforge Gaunlets to Soulforge Belt and Soulforge Gauntlets talk to Deliana in the Throne Room area of Ironforge to start Quest: A Supernatural Device, which leads to The Ectoplasmic Distiller, which leads to Hunting for Ectoplasm, which leads to A Portable Power Source, which leads to A Shifty Merchant, which leads to Return to Deliana, which leads to Just Compensation