My understanding was, from reading a bunch about it as well, that he most likely used a Mighty Mite 1300 ceramic humbucker also called Screamer. That was a Super Distortion copy, specs over the internet state they're around the Super Distortion resistance as well 13 to 13.5 kohm, but the coils of the 1300 aren't as thick as Super Distortions, which would surely have an impact to the sound, which is easily seen if you google the images. I believe both are supposed to have a thick ceramic magnet. I found conflicting information about who was actually producing these for MM, should be Schaller, but some state it was actually Duncan. I don't think however MM actually ever built their own pickups, fwiw.
Oh and while I have no first experience with the 1300, owners compare it favourably to the Super Distortion, and state it sounds a bit brighter on the top end and leaner on the bottom. VH himself said so many different things it is nigh impossible to know for sure, though. Good luck.