Setting up a new bike

I just got a new bike and want to set it up as closely to my old bike as possible. Looking at the
geometry info listed on the two companys' website, the bikes have the same length of top tube (525),
and come very close in several other key measurments. Some of the measurements where they are
considerably different are:

New SA = 76, Old SA = 72.5 New Head Tube Angle = 72, Old Head Tube Angle = 73 New Front Center =
590.5, Old Front Center = 561 New Head Tube Length = 110, Old Head Tube Length = 123

I am assuming that the SA is the most important difference. Is this a good assumption? How can I
tell how far the saddle on the new bike needs to be set back relative to the old bike to make up the
difference? Is there anything other than seat for/aft that I could/should do to make the frames
match better? My goal is to be able to ride the bicycles interchangeably (one for racing, one for
training).