The choice of external mirrors is, for the most part, a question of personal preference as it was, as others have stated, a dealer or owner installation. Placement of the Lucas fender mirrors, as I understand, is at the top of the fender, just outside of the fender bead to allow the foot a small separation, at the point where the inner fender ends.
The Lucas fender mirrors were considered the traditional choice in 1964 and my selection for my new BJ8P1. However, actually using the far mounted Lucas fender mirrors was out of the question until my early 50s when my nearsightedness transitioned toward being more farsighted that the mirrors started to become even mildly useful.
Over the years, many have installed door mirrors and some have chosen closer fender mounted bullets. Although I do like the look of my Lucas fender mirrors best, I feel that they are impractical for anyone actually using them as a driving assist.
Good luck,
Ray (64BJ8P1)