There's a simple test you can perform so as to get the polarity correct before you install the pups. (It requires a cheap meter, and preferably, clip-on leads.) Attach the meter leads with red going to what you assume is the "hot" wire and the black meter lead to ground. Put the meter on its lowest DCV range. Hold a washcloth or towel up against the pole pieces so you don't chip the mags on a single coil, or a Stag Mag humbucker.
Bring a #2 Phillips screwdriver up against the poles. Then yank it away. For "Duncan-polarity", the voltage should pulse positive as you bring the screwdriver close to the poles, and negative as you yank it away. If you get the opposite, reverse the leads on this pup relative to the Duncan.
This works for any pups.