Contemporary A5 is not necessarily the same than the supposed "A5" of yesteryears... To me, there's much more consistency and efficience in the magnets of nowadays. I'vestill to find a modern replica with the same kind of erratic measured magnetism and inductive influence than the rod mags in the few vintage pickups that I've been lucky to measure...
Furthermore, a guitar from a given year can host pickups built previously, with inconsistent specs. The 1962 L Series Strat that i have in maintenance once a year hosts three transducers with different Gaussing, DCR, inductance and measured resonant peaks.
That being said, among Duncan products, I'd easily choose a simple set of SSL1's for a 1963 "style" tone: IMHO and IME, they are "close enough" (to the mid pickup of the L series Strat that I mentioned above, for instance, with its 6k and 2.6H. The last set of SSL's that I've mounted had the same inductance, even if its DCR and Gaussing were a bit higher).
FWIW. YMMV.