Very tempted by a Beat at the moment but would have to consider putting a bike engine into it.

My question is... what do you have to do to get the Beat roadworthy after fitting a bike engine?

1. Inform the DVLA of the changes?
2. Get it MOT'd again? (or is there a special test that has to be done?)
3. Anything else?

I've often wanted to know about this, and if anyone can shed any light it would be appreciated.

Thanks.