Have you checked the price of a short block from Metric Motors or Adsit?

It's probably worth doing a compression and leakdown test to check the rings. It could be that you have a bad turbo seal causing the bulk of your oil consumption problem. If you disable the EGR valve vent the valve cover breather hose to atmosphere, how much oil do you get from the turbo?

Sixto
95 S420
91 300SE
87 300SDL
83 300SD