I'm 6'3" ... well, actually 6' 2 3/4" ... well, it depends on what time of day I'm measured. Taller first thing in the morning and all that. My 34" slack inseam is pretty constant though.
Anyway, I suspect that 58.5cm would marginal for you. My 58cm Kestrel fits pretty good ... my 60cm Trek is a tad too big. Just last night, I put the Trek on the trainer and was playing with the adjustments, (just installed a new, differently shaped handlebar and it has a much different feel than my old bars). Felt I was reaching just a tad bit. Slid the seat forward, and still too far away. Finally, I rotated the seat post 180 and it now feels great. Looks stupid, but fits well and is a lot more comfortable now.
If I were you, I'd opt for a 60cm, but if you can't wait for new stock, I have heard it said that it is much easier to make a slightly smaller frame fit someone. (size it up), than it is to make a slightly larger frame fit someone, (size it down). Do as Jaytron suggested and run through the CC on-line fit calculator. You'll need a buddy to help you, it will only take 10-15 minutes total. Then, pull up the geometry of the frame you are interested in and see if it will fit. With today's sloping geometry frames and such, it is no longer accurate to say that a 59cm frame from manufacturer "A" will fit exactly like a 59cm frame from manufacturer "B". You really have to know your own personal measurements and then look at the geometry charts.