visit the driftwood sellers, floridadriftwood and aquarium driftwood (?). I cna't recall which, but one has a great library and talks at lenght about what makes good wood good.
Bad wood will leach oils that are toxic and can have rot that will make an ammonia/nitrite spike through the roof. Cypress is good, if old, not if new, I think.
Discus are so expensive, I wouldn't chance it with them. What fish will be in this tank?
Fish Ranch, off I-59 had a ton of Mopani wood that is fine and sinks right away. Some place on Bellaire or Westheimer had some, Village has some, Aquarium world has some.