The arms go with the surname of the original armiger - just as people adopt arms (and a heyphenated surname) under Royal Licence due to an arms/name clause in a will. Under what actual name were the original arms registered? If the full surname was “Howard De Baca”, and you have the necessary proofs of paternal lineage to the previous armiger, I see nothing to stop you using those arms marshalled along with your own assumed arms. I would suggest that if you follow this course of action, that you put the arms that are already registered with an Heraldic Authority in the 1st and 4th quarters as they would be the most senior in both time and legallity. Once you have done this, you will definitely have unique arms. Please let us know what you decide as this is an interesting aspect of heraldry that one doesn't see all that often.

Regards,.