Generally speaking a good antenna is mounted close to the center of the vehicle, this is because the vehicle tends to be the a good portion of the antenna field. The running board antenna's of the '30's worked well in the city, however, on the open road/country they did not.. Been there done that.
My '36 is a Deluxe so it was wired for three antenna options from the factory, cowl, running board and roof chicken wire. The original wire is a shielded, braided wire with push, lugged connectors.
My radio has always been hooked to the antenna in the top, it has always worked great especially in urban, open road situations. During the mid 50's I added an antenna to the right side of the trunk area, quite close to the juncture of the car top and trunk area. This antenna is the concealed type that is only three inches above the body when it is down. Interestingly, the antenna makes no difference to the reception of the radio signal when the antenna is extended.
My '39 convertible has an antenna that is nothing more than a wire that leads up to one of the top bows... Works good.