1990 Vanagon Automatic Seeks Help!

I've got a terrible oil leak going into the cooling system somewhere
inside the engine. As in somewhere between a pint and a quart of oil
per mile!

The oil is coming out my cooling system overflow tank and onto the
ground (and, of course, the oil level is going down as this happens).

I've got over 190,000 on this engine, with new heads & gaskets back
at 88,000 miles.

Any suggestions for a possible cause & fix would be greatly appreciated.

Thanks,
Paul

Pictures of my VWs:

http://www.phonyexpress.com/images/VWs.jpg

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'90 Vanagon (190k)
'84 Vanagon (218k)
'78 Microbus (175k)