I would be cautious about using any oil additives unless they are specifically designed for break in duty.

Also - don't even try to start it till your burb is ready to drive (brakes work, cooling system road ready, good tires, steering close enough to drive) etc. Ask Tony P how many smokey engines he has seen from "driveway break ins" instead of properly seating the rings by working the motor as prescribed by the ring manufacturers.

Most of all - keep an eye on oil pressure and engine temperature once you do start it up. Don't want to have to rebuild your rebuild any time too soon.