I've never seen any fuss regarding matching Vin on frame and engine. Never seen a Vin on a bikes engine anyway. The title is matched to the frame, and if it's legally registered as a motorcycle then the engine or the amount of power it produces is a non point. Mopeds would run into issues because they have specific limits on output and maximum speed.
Funny, I got pulled over once doing 10 over and the officer was just impressed that I was maintaining over 50. Pulled me for a tail light bulb, gave me a warning. We talked about moped clubs, rallies, etc. But, when the topic of modifications and max speed came up he said that because I had a MC endorsement on my license that it was ok. Completely false but like hell was I about to argue.
I'll never forget him saying "man that thing can really boogaloo".