The shut off is a vacuum in either case, but there is a small difference in that the 85 has a different transmission and there are some small items that are associated with that that the 83 doesn't need. Basically the 85 engine will fit the 83. But the turbos are probably different, the 85 uses a vac assist to control shifting, so you would need the 83 turbo on the 85 engine to make it fit your car.
The '85 torque converter is also desireable for it has a higher stall speed spec.

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'95 E320 Wagon my favorite road car. '99 E300D wolf in sheeps body, '87 300D Sportline suspension, '79 300TD w/ 617.952 engine at 367,750 and counting!