Nice find!
Very good idea to leave the whole drivetrain just assembled as you have it -- for converting the gas car to diesel, fastest and easiest way is to just put the engine and trans in from beneath with the crossmember attached. I just did that same thing converting a 1986 740 turbo gas wagon and found it much faster and more elegant than installing the drivetrain topside. See pictures below.
Also, from the parts car, be sure to get the important parts of the diesel fuel system as well! Most critical is the fuel filler neck assembly. The diesel filler neck is larger and does not have the vapor-catch flap, so that it can admit the larger diesel fill nozzles that stations often use. See picture below for comparison. The fillers are not hard to swap and, IIRC, are shared between sedans and wagons. Grab it regardless.
And yes, you will need the clutch pedal and its bracket, any cruise control vacuum/electrical switches related to the clutch pedal, the clutch cable (though you may want to replace with new), driveshaft with center support bearing and front and rear shaft halves marked to preserve their proper phasing, and most of the under-hood wiring harness bits.
Bummer that someone took the turbo, since they certainly will have trouble using it on anything else. I hope they left the oil supply and return lines attached to the engine? I have a couple of spare D24T turbos in good shape that I would be willing to sell. The irritating part is that whoever stole that turbocharger also stole the turbo-to-downpipe gasket, which is getting hard to find and will not be useful to whoever bought it. Too bad. You will be able to find one with some effort.
Fuel filler comparison, gasser on left, diesel on right. Good idea to get the filler cap from the diesel too. I can describe what I did to modify the fuel lines and venting system from the gas car -- that part is not hard, no need to worry about getting the tank and lines, just the filler. Plus the 960 wagons came with a nice extra large 19-gallon fuel tank anyway... which you will want to keep regardless.
And here is what it looks like installing a D24T drivetrain "module" from below... disconnect the front suspension and steering and it is a piece of cake. I did it without even unhooking the power steering hoses from the donor car.
