The full video just published a few minutes ago -
https://www.youtube.com/watch?v=BsyCPauO4P0
Gives a great inside look at the Mitchell synchronized transmissions that are built into original Model A transmission cases so you can't tell from casual appearances that the car is modified. Simple bolt-in synchronized transmission with no modifications or cutting needed.
Also- This is the video that the clips are from talking about keeping greasy fingers off the clutch disc, pressure plate, and flywheel surfaces being discussed in another thread.