i would suggest trying to isolate where the sound is comming from.
if the knocking sounds to be comming from the clutch/flywheel area, or the lower gearbox or diff area you will have a starting point.
try using a flat tip screwdriver and holding it to your ear hard against a selected peice of gearbox or clutch housing, and using it like a stethoscope type device. this will help to pin point where the noise could be comming from. obviously you would need to make the car make the noise while you are listening to it, to find the noise.
if it is comming from the flywheel/clutch area as suspected at this point, i would think the best course of action would be to remove the clutch cover and have a look inside. this will involve supporting the engine from underneath and removing the drivers side engine mount so you can lift the engine slightly to remove the clutch cover.
are there any knocking sounds with the engine running?
Jason

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'66 BRG Morris Mini Deluxe 60HP ATW
