Neutral light was a 79 addition so presumably that's when it came in?
The LH shift works quite well, considering the back of a fag packet design
Triumph made the change in 1975, and I think it was the same for Norton.
Another cocktail napkin design is how they shoe-horned in the rear brake cylinder. I've theorized that the shifter/brake lever side swap is what caused them to go to a disc brake; that is, by utilizing hydraulics, they were able to switch sides without making any major frame changes. But God help you if you have to work on that brake cylinder.