Steve Chambers seeks "a 36 hole Sturmey Archer AB 3 speed hub/brake, must be in good condition dated from 1948-1951 and I would prefer it if it was fitted with a standard 3 lug sprocket fixing..."
In my experience, the 3-lug or spline driver is a drop-in replacement for the earlier types; I've done this for an ASC hub from 51. Only the driver itself needs to be replaced; the various washers and race covers &c fitted fine.
Best wishes.
Harvey Sachs
McLean va