I'd bet 105mph bone stock. I hit 105 on my Deluxe and it just wouldn't climb anymore. I had a SE air filter and a power commander installed and saw about 112mph and seemed like it was still climbing very, very slowly. My bud with the anniversary Fatboy said he hit 120 on his the other day. Of course it has the 95 kit installed.
I have the Screaming Eagle Fatboy and have hit 118 still climbing but really slow. It is all stock. I have a buddy with the HD race tuner and a 2-n-1 on his and he can easily hit 120 on the speedo.
I too would be curious to know but not overly so. Mine's been up to 90 with no grunting to get there. I have a 2003 ZO6 in the garage that's been all the way to the top. After that experience a couple of times, I just don't feel a need to know how fast anything will go anymore, LOL!
BTW, the ZO6 is for sale. It's Torch Red / mod red. PM me if interested.
I don't know the top speed of the FB but the built 1992 softail custom I had reached decent speeds for an HD. I did 115 on the 10 frwy although my foot vibrated off the peg and hit the ground and at that speed with forward controls you can imagine the pain.
G