Actually, I can help with that. Messianic Judaism would not have a High Priest or a head because they believe that Jesus Christ is their High Priest and Mediator, and they worship the Father through Him accordingly. (This is articulated in Hebrews.) Messianic Jews, in RL, can and do observe most every rite of the Orthodox Jews except sacrifice and the use of a High Priesthood. (Normal rabbis and such are there, though.)A reformable head for the Messianist heresy seems more likely. The Judeao-Christian heresy is rather vague, I'm not sure how a head would work.
Also, a Messianic Jew would never call Jesus by his Latin and English name. In Messianic Judaism, Jesus' Hebrew name, Ye'shua, is the term. Likewise, they call God by His original names, like "YAHW", "Jehovah God", and "I Am". Any flavored text would read "Praise Ye'shua" and also use the same format as normal Jews. Messianic Jews still observe Jewish holidays alongside Christian ones. Their version of the Passover is slightly different in meaning, but not in the way it is done. (For more on the Messianic interpretation of the Passover, you can look up "Jews for Jesus".)