In almost any places, the police know little of the laws. Just saying under 50cc is usually sufficient, unless the cops are already dedicated to getting you a ticket anyway - then you're screwed regardless of legality.
points i'd make
1) your vin will be >50cc if they ever run it. If a vin is required for registration in your state, that will kinda kill the idea straight off. If you're in a state that just registers a moped as a moped, and theyre not doing VIN checks or requiring a title, you should be OK. I don't know for MN
2) It's gonna be underpowered if it's built to suit a bigger engine
3) The 2hp limit is not a hard one, they're not out here with dynos. basically it's just if they catch you going 50 they'll be skeptical it's a moped...
4) Just ride it as 125! It's going to be more work to swap it, less useful vs the benefit for registering a moped. If you've got a 125 motorcycle, that's a very easy bike to take a motorcycle test on, you've got much less to worry about and a more reliable vehicle - I think if you want the bike, whatever it is, it's gonna be the most sensible case to use it for what it is, as is.