Damn, I thought the Nichols website might have had some sort of answer but no go:
http://www.nicholsmfg.com/ducati-parts.html Other info is just as sparse - (shouldn't Baines be able to do it / tell you ???)
here is some advice from the Ducati.ms website
"My '95 SS kept breaking the studs (one at a time) on the horizontal cylinder. Foolishly I only replaced the broken stud. Weeks (or months) later another would break. Last one broke INSIDE the case (i.e. nothing showing out of the case, just the top of the thread!! At that point I decided to change all (on that cylinder) in one go. Never had a problem since.
Never had a problem with the vertical cylinder either - but just replaced them all when having a 944 kit dropped in.
I believe the 916 studs are the replacement item from Ducati"
Good luck - Frank