Why?
As I understand, you have a J-2 visa stamp. Now if your spouse's IAP-66 was initially issued for 3 years (mostly they issue first IAP-66 for one year on extendable basis though), most probably the expiry date of your visa stamp, too, is far away. In that case, you can come back on J-2 stamp anyway until it expires. Then why to complicate matters with B? While theoretically you might be able to use I-539 form for J-2 to B, it might not be that easy to convince INS for this kind of change of visa status, especially so in present post-9/11 era.
Also, keep in mind that once you change to B from J-2 (or if you enter the US on B), your EAD automatically becomes invalid even if its printed expiry date might be farther.
If I were you, I would use exisiting valid J-2 visa stamp OR re-appear for B in India (so that if consulate denies B, I could use J-2 if still valid at that time).
Best wishes,
Jigesh
Disclaimer: Personal non-legal point of view only.