what is this thing circled and is it possible that the oil leak is coming from it. there is oil everywhere. on the fan blades, hood, and oil pan has a stream right down the middle. vacuum pump also pictured, it looks new though, but also covered.

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That's the shock absorber on your serp belt tensioner. It doesn't hold a lot of oil, but it is just below the valve cover gasket and head gasket. the problem with locating a leak in this area is that oil gets picked up by the fan and flung around. How does the underside look?

Alternator, covered. Halfway back on the block, bone dry. Underside, covered. If I wipe the oil pan clean and drive it a few miles and look again (did so adjusting trans modulator) it will have a stream right down the center.

Front main seal?

Could be main seal or oil pan gasket. Not sure about a 124, but on a 201 the oil pan settles onto the sway bar when the motor mounts age. If that isn't attended to, the sway bar can wear a hole in the pan.