I recently got a mid-1990s Specialized Epic Pro road bike and am looking forward to getting back into modern cycling after twenty five years or so off. It's a carbon frame with aluminum (?) lugs and fork, and a full Dura-Ace 8-speed groupo. Since I'm not in shape
yet 
, and since it's pretty hilly around here, I need to get a little lower gear ratio on the lowest gear(s). I believe that it currently has a 12-24 cassette. I'd love to be able to get two gears lower than the current 24, if possible.
My question is, what is the max number of teeth that my Dura Ace RD can manage? Sheldon's site seems to indicate 27 in some places and 30 in others.
At this point I'm not really interested in converting to 10 speed or replacing the crank; I don't want to get into that kind of cost until I have a few more miles on the saddle.
Thanks in advance for any help!