The later model switches are among a modest list of small parts that can give rise to another level of sub-projects, with their attendant delays & added cost, where purist-type restorations are involved.
The K3 switch unit is unique... difficult, but not impossible, to replace/restore. WTF even knows what handlebar configuration is "correct" for any year/model prior to `79? Even Honda couldn't get the same configuration every time. As for OEM mirrors, 2 more rare parts that would be an expensive nightmare to restore.
It's up to guy doing the project as to whether to cost & effort of sourcing/restoring original parts is worthwhile. With a restomod, or custom, the correct part is whatever the owner says...unlike a purist resto. :39: