I normally ride a 58cm road, didnt fit on a 58cm tri, felt a little too stretched out on 56, but felt very comfortable on 54cm....you should be good on 58 cm, that's what i recommend, if you dont feel good, i'd may even jump down to a 56cm, but it will be a stretched out 56....up to you, 58 should be fine, but when in doubt, go try more out.
Im a poet and i didnt even know it YO!