[lmsport]

if the block was align honed or align bored, the step bore that locates the rear seal will have the same ID or larger as the main bearing bore. will be hard to tell in an assembled engine.

 

[lmsport]

are you sure the seal is installed correctly?
is the crankcase vented?
the lack of sealer on the rear cap can be a good size leak, depending on the exact surface condition of the block and cap.

 

[lmsport]

Fel pro has a seal with an offset seal lip in case the crank has a groove. Only works with a non-aligned main block. the Fel pro 2909 is the only seal for a aligned block.