OE Mercedes OM617 Naturally Aspirated-Diesel 5-Cylinder 3.0L Motor with only 180,000 original miles.
It was pulled from a W460 300GD G-Wagon, so it has the heavier-duty oil pan. In order to fit into the W123 chassis, this engine would need its upper and lower oil pans replaced with the oil pans from a W123. We have these available for sale separately. 
This is the later style with smaller pencil-style glow plugs. Models from 1979 and earlier will need some glow plug wiring modification.

Compression Numbers for this engine are 400+ on all five cylinders.

The specialized G-Wagen OM617 engine support arms, and the specialized thicker flywheel are not included but are available for sale separately (with used clutch included).

The 4-speed manual transmission is available for sale here.

Included in the sale is:
Long block (oil pan to valve cover)
Injection Pump, Fuel Filter & Attached Components
Fuel Injectors & Lines
Exhaust & Intake Manifolds
Glow Plugs
Oil Filter Housing
Vacuum Pump
Water Pump & Thermostat Housing
Throttle Linkage

Other Components Not Included, Available for Sale Separately:
Air Cleaner Box
Alternator
Oil Cooler
Glow Plug Relay & Wiring Harness
Power Steering Pump
Starter
Cruise Control Modulator
Radiator

Shipping will be LTL freight. Please contact us for a quote; it will be roughly $350-$600 depending on your location.
We will ship internationally although it may be very expensive; if you have a serious inquiry please contact us for a quote