amrein,
If you are talking about the NAND backup (SYSTC860.DBK) then yes, you have to rename it to SYSTC760.DBK for the C760 to recognise it.
After the NAND flash, your service menus will be red - don\'t know of they are normally red on the C860 or not. Also then you will need to use the C860 updater.sh as your machine will be identified as a C860.
If you are talking about the backup done with backup/restore app then yes again, just rename the file again.
If you are talking about other roms, then most probably will aslo work.
Stu