Several good ways to go. Brad Penn breakin oil is good and Joe Gibbs racing oil & this 5 minute read may interest you. "breakin secrets" at www.mototuneusa.com
I have used Joe Gibbs BR break in oil. It' not cheap but its loaded with zinc for our flat tappet engines. You will probably have several hundred or even a few thousand dollars in your build so do cheap out on the oil.