This is simple.
Mostly about people and business decisions not technical aspects.
All good news from my view..
You have the bike at Dragos.
Frank is a very sharp dude and what he does and says works and is not costly compared to the market, simple.
You are polling for opinions on a forum and really all you need to do is set your horsepower and reliability expectation and let Frank drive.
He presents you with options and you decide, simple.
If you want a rock solid 124" motor buy the S&S and if you have hopes of selling the bike keep your motor and swap it back in, simple and cost effective. On the resale market the new motor will be neutral in value for the most part but as a part on it's own would still carry 50% resale value. The used 110 is not going to bring much.
Build options range from a little messing with the 110 (120hp easy), a 113" upgrade (125hp), 120R (130hp) or the 124"(135hp). Once again Frank can lay it out for you and save a lot of vacillating plus make his job a lot easier. The horsepower numbers I cite cost more as you move up the line of course plus these are in street trim, reliable configuration, and relatively conservative.
State the horsepower, get the quote, decide, he implements the changes, you pay and ride on happy, simple.
Trust him, you won't be sorry.