Exchange 2007 – Exchange 5.5

I am migrating from 5.5 to 2007. As we shut down remote Exchange 5.5 servers, can we update existing 5.5 GAL’s with data from 2007 GAL’s? New users to 2007 now are being added to 5.5 so that addresses will show. Is there an efficient way to update GAL’s in 5.5? Please help.

Thanks, Gerry