Long story short...I scored a Copperhead 12. Engine is locked up, frame is in awesome shape. My conundrum now is to repower with factory LCT 12hp, or go get a Predator 22hp. I know the 22 will bolt up, but the question is what would I have to do to make it work? Thanks.

Shaft height will likely be different requiring a different belt length and different prop.
I'd go with the 14hp and add a stage 1 hop up kit.

You'll come in at less cost and have more power going the V-twin Predator route. Call Copperhead. Tell them what you have, and tell them what you want to put on it. I'm sure they'll help you get the right parts to make the change.