On the 64, and 65 for that matter, you had three
radio options (not counting the reverb). Standard was a Motorola AM
radio, with a single 4x10 speaker in the center of the dash.
Radio model was 4TMS, or 5TMS for the 65. Optional was a rear speaker. If you look at the back seat, the bird
emblem above the center armrest has louvers around it. If it's solid, no rear speaker. If you have the louvers, the car has a rear speaker option. Speaker is 5x7.
Radio model is 4TMS/F, or 5TMS/F, signifying the
radio has a fader control behind the tuning knob.,
The third option was the AM/FM
radio, which includes a fader control and a rear speaker.
Radio model is F4TBS for 64, or TOB5TBS for 65.
The reverb option disables the fader if equipped, and adds a switch/control under the dash to control the echo through the rear speaker.
To elaborate a little more on my former comments, Bendix radios from about 1955 through the mid 60's are awful sets. They were used in late 50's Fords and Mopars, and AM/FM sets from about 1962-66 on Fords, Mopars, and a few others (except 1966 Lincoln, when they got smart and switched to Delco. So did Chrysler in the late 60's.
The late 50's Bendix AM sets were okay at the time, but the components go bad over time. These sets are notorious for intermittent problems -- hit a bump and reception fades, hit another bump and it returns. You will tear your hair out trying to fix it, and most shops won't touch them. Same with the 1962-66 AM/FM sets, but these sets have additional goodies, like germanium power transistors that blow, cost $50 each to replace, and blow again if you don't track down the bias problem that causes it. The "Second generation" Bendix AM/FM's (starting in 1967) are a big improvement -- still nothing to write home about in terms of performance, but much more reliable.
I might add that, yes, I do conversions of old radios to AM/FM Stereo. You could look at it two ways. Either my answer is always going to be a conversion, or this: I got involved in the conversions because it's the best answer for a lot of these sets. Some of the older radios, such as 1950's Buicks, are really good sets, but of course they're AM only. So I'm filling the need.