Oil leak in turbo van

Hello everyone,
My stock 89 Turbo 2.5 van developed a pretty bad oil leak on the passenger's side of the engine. It seems to be below the midway point of the cylinders on the block.... I'm thinking this is either a bad oil pan gasket (Which I replaced last in 2006)
or my intermediate shaft is leaking... Which is more likely? The engine has 226,000 miles on it. It is making this horrible noise of a bad bearing, but only in the very cold weather. But I think that is transmission related (520)

What is the best way to tell where I'm leaking without just replacing the oil pan gasket?

Check the oil return hose coming from the turbo to the back of the block.

If you tear down the belt side of the engine, you should be able to see where the leak is. My bet would be the aux shaft seal or crank seal is bad. The rotating parts, crank sprocket and aux shaft sprocket sort of just wing that oil in all directions. Only down side is the timing belt needs to come off to change either out. The crank sprocket requires either a special tool or the ability to make your own tool to remove, if that is where the leak is. With that many miles on engine, they probably should both be replaced.
One other place to look for a leak is the oil galley plug located directly behind the aux. shaft sprocket. That is a 5/8" core plug. Those can leak too. Here is a couple pics for you. In the last attachment, you can barely see the core plug sticking out past the top of the aux. shaft sprocket at about an 11 o'clock position behind the aux shaft.
Good luck,
Todd