I suggest leaving it alone.
The requirement for a case bore, crank work, and all the other costs adds up. It's not much more to go to 124" with an S&S kit and your heads worked. Why dabble. Wait and get it done once and right.
x2. That's the best advice so far.However, Rev Performance has another option.
http://revperf.com/. I wonder if Dewey's or Hillside have any experience with these?
They have a 113 kit that is a direct bolt-on with granite cylinders and S&S 10.5 pistons. No splitting/boring the case involved. It's a simple install. I had piston slap in my stock motor, and the 113 kit really quieted that problem. Burned less oil, too.
But just the big bore kit alone isn't going to make a huge difference. You'll need head work, the right cams and exhaust, maybe a TB, and a dynotune done by an expert, to really make a difference.
Good luck with whatever you decide!