Channel mapping is wonderful - but never so wonderful as when you have actual channel maps!
HS-64-TETRODE-ADAPTOR-MAPPING.PDF below is the map to go from the white matter 64ch EIB to the eCube HS-64 headstage
Besides, the file named "Channel_Maps_Scanned" contains channel maps for 32 channel omnetics (NLX) assembly and EIB_88ch_OpenEphys_drive_V1. Enjoy!