Do you have time to remove the air intake snorkel? That should allow more even lighting. Maybe hold the camera against the air cleaner barrier and shoot blindly towards the thermostat.

There seems to be some oil where the mixing pipe attaches to the head. Oil there can only come from a leaky valve cover, which looks dry.

Oil on the thermostat and alternator probably comes from the chain tensioner or #1 exhaust runner. Or, and hopefully not, the new head gasket isn't holding around the typical failure point.

Sixto
87 300D