Not wishing to throw a spanner in the works, but the 3690 figure is shown against 818.540/541, In La Lancia this is shown as a 2nd series 1600 HF, 1969-1972 (does this make it a series 1?) it also shows 818.740/741 as a second series Sport, which it isn't.
So, are they both 2nd series, which would alter the figures?
Actually, as you've previously pointed out the figures in La Lancia are screwed up (I think that's the technical publishing term); they're better sorted in Weerninck's The Lancia Fulvia and Flavia, A Collector's Guide (which is what I quoted earlier), and they're correctly sorted in Altorio, as follows:
1.6HF (S1 'Fanalone') 818.540/541: starting chassis 1001, 1258 produced (+ a later 20, all 818.540 for works use).
1600HF (S2) 818.740/741: starting chassis 1001, 3690 produced.
Sport 1.6 (S2 Zagato): 818.750/751: starting chassis 1001, 800 produced.
In Apr 1996 C&SC, Martin Buckley reports that 30 RHD Fanalones (818.541) were produced as 'Lusso' models (bumpers and metallic paint), but doesn't note how many total RHD Fanalones or 1600HFs (818.751) were produced. BTW, if you think it's tough to find RHD production figures, try finding out how many Lussos (either S1 or S2) were produced. I'm entirely sure that both eyore and Neil Cundy are correct: not all RHD cars (either 818.541 or 818.741) were shipped to the UK; Oz and SA both received some.
But let's
not start on colours, shall we?