Don't forget that there is a difference between a two way radio transceiver antenna and a plain old radio receiver antenna. All a regular car radio needs is an antenna that will receive signals of a frequency range depending on the receivers frequency band. An AM radio only needs a simple antenna and any coils will usually be inside the radio set.
A transceiver antenna can be a bit more complicated.
Ignition noise, generator noise, or what have you, can be filtered with a capacitor in the noisy items power line. The King Seeley senders sometimes had caps on them too.
The Motorola 60 was not a Ford standard option. The Motorola 60P was actually a police radio made from the model 60 and they are kind of big in either case. They were a reciever and they did have a load coil system. Here is a link with some info.
http://www.wb6nvh.com/Moto/Motadata.htm
They mention a magic eliminode system for these. The eliminode system was supposed to be a noise eliminating dual antenna system with one antenna to eleminate noise and the other to pick up the radio frequencies. I don't think this system lasted very long. Here is a diagram link.
http://www.nostalgiaair.org/PagesByM...2/M0006702.pdf
Car radios were still kind of a new thing in the mid 30s so a lot of different things were being experimented with. Those Motorola Model 60P receivers were likely among the first police band receivers put into wide use before Police bands got out of the AM frequencies and went to VHF.