This is really exasperating, and I need some fresh ideas.  I did a
top-end rebuild on a Chevy 350 that's in a 1984 K-20 truck I recently
bought.  It had a pretty good oil leak at the rear of the engine, so
last weekend I dropped the oil pan, cleaned everything out, and
installed a new rear main seal, high-volume oil pump, and pan gasket.
And it still leaks.

The two sender holes (one next to the distributor, which is connected
to the OP gauge, and the one above the oil filter) are properly sealed.
It *looks* like oil is coming from the back of the block, and anybody
would tell you at a glance that it's the rear main seal.  But we know
it's not that because there's a brand new seal installed.

Is there an oil gallery plug or something at the top rear of the block?
I just gunked and pressure washed the whole engine, so presumably I
might be able to tell where the oil is coming from.

Did I miss something?

Thanks!