You can export your 878 data using the CPS software and then import it into the 578 using the CPS software for that radio. Go to Tools>Export and click on Export All. It will save a file with a .LST extension and export all of your files as sepaerate .CSV files. Then go to the 578 CPS and select Tools>Import and click on import a .LST file. It will bring in all of your CSV files. You might get some errors (I did) but I got my Channels, Zones, and Contact List and that was really all I was interested in.
Worth a try.
GL - WA9BD
WA9BD