The tail light you show there is a 90/110/Defender light. There is a significant difference from the Series lights - the Series ones incorporate a reflector, coil sprung ones have a separate reflector, so if you keep these lights you need to provide a separate reflector. There were about four or five different tail lights fitted to Series 2/2a, and none of them are easy to find, and probably harder to find out what was originally fitted.

