In Britannia, as others have pointed out, NO pilots flew both the -200 and the -300. All the -200s were to the same flight deck config as the very first one delivered in the late 60s, with no retro fits when more modern navigation instruments became available.
Not quite. The first addition to later buys was HF; then, rather later, PDCS and Omega. I was surprised to find that we were allowed to go to the Canaries with no long-range navaid - and that in the days when Porto Santo still only had an NDB. We would leave Lisbon radar cover before the Porto Santo NDB became useful, so the navigation for a while was point and hope. On one N'bound return sector, I remember Lisbon telling us we were 60nm off track on entering their radar cover. The Omega was often not too clever, probably because the BAL fit used an ADF sense antenna and not a dedicated one. One year we had a couple of leased-in Canadian B737-200 (Quebecair?) which had Omega with a dedicated antenna - and that worked much better.