I have actually read about some 98 ss and pre 97SS frames cracking, trying to dig up the article. IT did not state why or where but there is a list also I looked at, not that this is a bad deal or what not. definitely not what I am saying , just trying to offer an insight as to why so you can approach the challenge correctly.
Just before trading my 900SS for the VTR, its frame cracked. Seems like there are a good number of occurances of SS cracked frames on the Ducati list. Seems to affect pre `98 or pre `97 SSs. Another issue are the 4V rocker arms on 748/916/996 models. I got a used 916 with 9000 miles... and right away, I found that the rocker arms were bad!
this is a quote from an article here
ducati tech buyers FAQ
again this is not meant to be a detractor or negative in any way, I am simply offering some reference so you can make the most out of the purchase if you go ahead.
I was a Ch47 and MH47 mechanic and air crew in the army for half my life and while many stressful things occur for many varied reasons, the why is always the most important variable moving forward. This is not to say that a bike is like a helicopter. However they are both high stress operating technical pieces of equipment that can ( and in helicopters case, mostly) result in death if they fail critically. I have walked away from two crashes of each motorcycle and helicopter ( although if no one dies in helicopter they tend to want to call it a hard landing) :/ go figure. funny story they offered me an MOS change etc. after the first one and I said nah I love this what are the odds of it happening again, uh huh.
Regardless, remember the why and if I can find that list of reasons and locations of failures I will post it. If i can recall the cracks and breaks were in various positions. Head tube @frame, subframe under seat, main frame at subframe mount, and various other locations. If you ride a lot you can almost narrow it down to a small list of reasons these could occur. once you rule out rider error and abuse then you can look into mechanical reasons for failure.
no matter what you ride - you should always check you equipment for stress in the areas that get stressed, motorcycle thats more than 80 percent of it. and if the only thing you do with it is ride it on a groomed race track at performance levels, then you should check it 2 or three more times LOL. if it is a dirt bike then every part s is definitely a stressed part.
anyways sorry for the long diatribe, I don't chime in much. I know a bit about mechanical and structural engineering and thought i would offer some basic advice.
on a side note the rest of the parts look good, you could always go full on and put the motor in another type or style of frame and really make it a monster - Frankenstein style - it's frahnkensteeen damnit!