Chosen Solution

Will a Mid 2009 to 2010 replacement battery work with a late 2008 to early 2009 model?

Sorry no, The older MacBook Pro 15" Unibody (Late 2008-Early 2009) Battery is a user removable design unlike the newer MacBook Pro 15" Unibody (Mid 2009-Mid 2010) Battery which is a serviceable replicable design. The sizes and the connections are very different.