you might also want to get the "saddle nose to BB" measurement. Once you've gotten the saddle height set close, gettting the saddle into the similar fore/aft position will put you closer to where you were on the old bike. You're actually concerned with the sitzbone placement relative to the crank/BB position, but since most road saddles are within a few mm of length, saddle nose to bb is the easier measurement. CAVEAT might be some of the newer saddle shapes like the Adamo...
to measure : make certain that the bike is on level ground (even a 'flat' concrete surface may not be level - my garage floor slopes markedly from front to back)
drop a plumb line from the saddle nose, making sure to allow the line to properly find 'plumb', letting it hang against the crankarm can cause it to not hang properly.
measure from the hanging line, in a horizontal plane, to the center of the BB/crankarm
replicate on the new bike - making slight adjustments for any change in crankarm length from old to new...