There were various types of 320C aircraft. Some seem to have hauled the cargo door and strengthened floor about with them all their life without ever getting put into the cargo configuration - for US carriers I believe there was a federal subsidy to do this to form part of a reserve military capability, but others overseas did the same. Some were configured internally for cargo, but retaining their wndows. Then there were cargo-configured aircraft which had plugs in the windows, and depending on how well the livery had been applied you might think they had none, but they could be converted back over. I think the Pan Am ones were like this. Lastly there were I believe those built by Boeing with no window apertures, which restricted them to cargo operations for all time. There weren't many of these but I believe the American Airlines freighter fleet were like this.
Did BOAC use the plugs ?
In passing, when a cargo aircraft was delivered to BOAC, did it come with all the cabin furnishings ? Were they kept in store somewhere ready to be used ?
there was a longish gap when BOAC didn’t operate West Coast nonstops. In the 60s they had used 436s on San Francisco, which was at the limit of their range
My 1962 BOAC timetable shows a 707 service BA591/2 several days a week to Los Angeles with an unspecified "technical landing" (which I am guessing might have been Winnipeg). These would be the original RR 707s.
By my 1971 BOAC timetable, Los Angeles was now served by a daily VC10, still BA591/2, which operated through New York. This was the through transpacific flight from Sydney, which eastbound departed LAX at midnight, and formed the morning "daylight" departure from JFK to London. Can't have been very competitive with the Pan Am/TWA nonstops.
This was replaced in BA times in the mid-1970s by another curious arrangement, where for some years BA chartered daily an Air New Zealand DC-10 operating through LAX to London, with full BA crews (I believe they went from London over to KLM at Amsterdam for DC-10 sim sessions). BA wouldn't use their 747-100s to the West Coast either, despite the US carriers doing so, it wasn't until the first 747-200Bs came along in 1978 that they changed over LAX and started San Francisco. Being a regular pax on the route then, I was on one of the last DC-10s and also one of the first 747s.
Sorry, long way from 707s !