The M8 107, 114 and 117in engines are basically big bore engines! You don't need the big bore kits to get great performance. I have the S&S 550c cam in my '22 114in Fat Boy. Oustanding! Definitely my favorite cam!
A little hesitant in the really low RPM's. 2,000-2,500rpm it smooths out. At 3,000rpm the 550 cam comes to life. Starts to scream. Pulls hard straight through 6,100rpm.
Now You're Talking!! Next level.
These kits, without headwork, come in at around 135hp. More if you add intake and throttle body. Perfect for a stock crank. 140hp max.