The 366 at the end of any Artex 406MHz ELT simply indicates that the unit is programmed for the USA serialized long message format. All Artex 406 ELTs (C406 and G406 series) except for the ME406 are shipped from Artex with the 366 programming unless you specify otherwise. For international applications, once the ELT is reprogrammed, the unit dataplate and box label is updated with the new programming information. An updated FAA Form 8130 is issued at this time as well.
Therefore, if you are searching for an Artex 406 ELT ending in the -366 such as 455-5015-[366], then you can use the base number (ex. 455-5015) in most cases.