I absolutely agree with the comments on Airfix' Bismarck; the greatest
insult is probably the hull which is totally out of shape.
However, the Revell Bismarck, while having a much better hull, comes
off even worse as far as superstructure and armament is concerned. The
forward superstructure is totally wrong, main and secondary turrets are
abysmal, heavy AA even more so. The secondaries from the Scharnhorst
kit are much better (even though they need reworking, too).
Currently no acceptable heavy AAs are available in 1/600; those in the
Airfix Prinz Eugen kit were an excellent starting point (a good source
for other useful parts as well, like a decent aircraft, light AA guns,
searchlights etc), but sadly that kit has been out of production for
quite some time now. The 105mm in the Airfix kit are unuseable, as are
those that come with the Revell Bismarck/Tirpitz. The Scharnhorst
pieces aren't much of a help either, but might possibly be modified
into something looking remotely like the real thing.
So a 1/600 Bismarck is indeed a momentous undertaking. Starting with
the Revell hull one would need some Airfix superstructure parts,
reworked Scharnhorst secondaries and either spares from Airfix Prinz
Eugen kits or a host of scratchbuilt small parts.
There is one other option: the Monogram box scale Bismarck/Tirpitz
which scales out at around 1/600, perhaps a little bit smaller. I don't
know about the availability abroad - it's extremely rare where I live
at the moment - but overall it is definitely the pick of the bunch.
Jorit