What is the diameter of 1B9101?

Hello, I have a 1972 Austin Mini 1000. The right front turn indicator stopped working so I went to change out the bulb in both front indicators. WHen I did this I learned that the previous owner must have changed out one of the assemblies since the left side uses a different bulb then the right side. So I am going to replace the entire indicator assembly on both sides so that the bulb type will be the same for future replacement. Will this assembly fit into a 1972 MkIII Mini? Also, the glass lenses I have are in good condition. Can I swap out the glass lens with the plastic lens that come with this assembly OR do I need to purchase a glass assembly? Thanks you for your help. Kind regards,