I have a late 1953 M33, so same engine. I've found that oil leaking from the engine, even from the front right, very often finds its way to the primary drive cover just under the clutch. It drips on the ground when I stop, and this makes it look like a primary case leak. If my primary case does leak oil, it's pretty minimal.
The breather is in the timing chest cover, pointing backward and down at about 45 degrees. There's a little disc inside that moves back and forth under crankcase pressure. If the breather gets blocked because, say, the disc is stuck, you will have more than a little oil leak!
