Thanks Walt, so far so good. I hadn't considered that it may be warped.
Actually I pulled the engine/trans today for other repairs. As for the oil leak, it appears to be the breather hose and maybe the thermostat.
Funny thing is - the hose is new, as is the thermostat o-ring! I changed them when I refurb'd the CIS. Clamp on the breather hose is tight, so what gives??? I did have to tweak the hose a bit when installing, but seems unlikely that would cause it to leak. Any thoughts? Is there some trick to getting this hose to seal?