That's my issue too. I'm afraid the stock 120 won't be enough without major headwork, then a different piston to get the compression back up, then cams, then beefed up crank, bearings and flywheel or whatever. I know going from a 96" to a 110" seemed about a 10-15% increase in power. If a 110" to a 120" is another 10 or 15% I wonder if the price for the 120 would be better spent on a custom built that I would keep and swap as I trade up in model years. I dunno, I just want to do it right the first time instead of "I wish". Buy a set of cases, axtell jugs, bomb proof crank, worked heads and recommended components to go with them?...