Don"t dismiss the back of the intake manifold where it mates to the block. Had a leak in mine that appeared to be coming from the bell housing so I suspected the rear main.
After tearing everything apart and removing the bell housing, clutch, transmission and flywheel found the rear main seal area dry. Ended up putting the fly wheel, bell housing and starter back on and using trace dye in the
oil. After running the engine for about 15 minutes got another couple of drops of
oil on the bottom of the bell housing but still couldn't see where it was coming from. Removed the starter, bell housing and flywheel again and, when I pulled the rear engine plate finally noticed that there was a trace of
oil coming from the rear of the intake manifold.
What surprised me was that the oil seep was so small it hardly showed up at the rear of the manifold but it was MIGRATING ALONG THE JOINT BETWEEN THE BACKING PLATE and the block all the way around until it got to the bottom of the bell housing and then it would drip off.
DonC