I put the TKO on the back of the 20B today and dropped them into the engine bay to measure up the gearbox cross member.
Sorry I don't have any pics at the moment as the missus is away and she took the camera and my phone is no better than a potato.
The TKO fits the RX4 transmission tunnel very well and shouldn't need any "clearancing".
I have measured up and modeled the gearbox cross member.
Turns out to only need a very simple design
.