Forget the 122. That's intended for certain Hammond models only with a balanced audio input.
If you want a single channel, twin rotor valve/tube leslie, then the 145 is the one to go for. A standard 26-1 connector kit such as the 7279 will allow you to connect the leslie to the organ's Spectratone channel. This will leave the non Spectratone voices, such as the rhythms, pedals and Orbit synthesizer, in the organ console. You don't need the extra height of the 147 cabinet as it will not be handling any bass. Of course, the 145's twin rotor tremolo isn't quite the 'theatrical' tremulant that some would say the organ needs, and they perhaps have a bit of a point in that. A less expensive option would be a 125 single rotor leslie, or even a 120 or 110. These two have no amplification of their own, but you don't necessarily want that, as you need to keep the balance between rotary and non-rotary channels. All of these would use the same connector kit as the 145.
If you want a multi-channel leslie that would handle both rotary and non-rotary channels, then you're looking at the solid state models (nothing wrong with that!) like the 700 (single rotor), 710 and 715 (both twin rotor). You'd need to cobble together a connector kit for these, but it's not really rocket science and has been discussed on here many times. These cabinets have some real oomph to them, something that you may or may not need.