Check the detail of your state antique motor vehicle regulations. I found that, in the state of VA, two plates are required except "...antique motor vehicles may display single license plates if the original manufacturer's design of the antique motor vehicles allows for use of only single license plates..." I carry a copy of this section of the Motor Vehicle Code in the car, along with factory photos showing the front of the Avanti sans plate or mounting bracket. I also carry the second plate to prove that it is not being used on another vehicle. Perhaps MD has a similar provision in their code.
Truth be told, I've never had anyone question the "missing" front plate.
If one felt compelled to use a front plate, a very simple bracket can be made to go behind the center rubber insert, to hold the plate just below the bumper. A slightly more complicated design could include a piano hinge in the bracket to allow the plate to swing back under the bumper for display purposes. For you James Bond fans, the plate could be remotely deployed/retracted via a solenoid or cable mechanism. 😉