I don't know if you can even get the dual point Mallory any more, the Unilite that Colorado66 has is probably the way to go, I'm looking to convert mine to electronic if I can. I will get the number if you're interested though.
Someone here may be able to answer the question also of if you run any vacuum advance, where you source it from. When I purchased and installed my Offy years ago, Clifford said that I had to use a mechanical advance distributor and the original vac. advance would not work, so I never tried it any other way. I think maybe the thing to do is convert a DSII as Jack outlined, maybe get yourself a second distributor to convert.
See Ya,
Mike