While most sources say the DiMarzio H-3 was in the prototype jag-stang it in fact had a Dimarzio H-8 in it. (H-8 info at bottom)
If you are wondering, the H-3 does exist. However it was made exclusively for Fender and not available as a retail item. The DiMarzio Evolution Neck model (DP158) is the closest sounding pickup available individually.
The H-8 was also a Fender exclusive pickup and not available retail. According to DiMarzio the PAF Pro (DP151F) is the most similar pickup available retail.
Here is an interesting note and pics I received from Earnie Bailey on this very topic.
I saw your page about the Jag Stang, it’s great ! Mark Wittenberg stated somewhere that Kurt’s JS came stock with a H-3, but it was actually a H-8. I swapped it out for a white Duncan JB the day before the did “MTV Unplugged”, along with Kurt’s other blue Japan Mustangs.
Best regards, Earnie