I was looking at this Doka on eBay.  My favorite line in the description
was:

"When the very tired engine I bought it with gave up the ghost, I had it
replaced with a used one that was gone over very well by a trusted mechanic.
Being a detail guy trained in VW's he went thru the engine without taking it
apart and made sure it would be a solid runner."

He must be one hell of a good mechanic to be able to "go through" the engine
without taking it apart...

Cheers,

Jeff