rebuilt engine leaking oil....

[Austin in the Shed]

Er, normally, yes.
Just check, there’s supposed to be an oil drain hole at the bottom of the steel bearing housing.  It’s important that the carrier is fitted the right way up because it will go the wrong way.  I only mention it because I can’t see it in your photograph.

The reverse scroll rear bearing cover normally holds the oil in unless as said the oil drain hole isn’t at the bottom of the housing.Why has it got a ball race at the rear,is it a wheel bearing?
Stuart Rolt used to use two self aligning double row ball races but with this arrangement how does the crank grow and shrink in length when whipping ?
If indeed the oil has come out of the back of the crank you must have had a bell housing and clutch full of oil ?