You can go all the way up if you are willing to pull the motor and have the cases bored. Budget must be there to support the build. In my experience a properly built Twin Cam 124", for example, will cost as much to build or more than a similar crate motor. Not a fan of the crate motors and not for profit reasons, I can sell either. The 124 would require a very stout clutch and supporting hardware. Me personally I prefer a 117" because of the longer piston skirts and shorter stroke in terms of longevity. But we are splitting hairs now and the cost is the same.
The best bang for the buck, in my opinion, is all the way down the spectrum at 110" which is a top end job, engine left in chassis. It is not hard to hit the mid 120s squared with good manners and longevity. The S&S 110 kit is where I start that build.
A lot will depend on how you ride and what you want to accomplish. This is where the discussion should start plus what you intend to spend. Then after the build plan is done who will tune this and what pipe to buy.