From your current position, I would suggest removing the rocker stands. By doing this the valves will stay closed. This will allow you to get the chain back together and be able to roll the motor over. Do that first and then with them still off set the crank on one and pull the cam gear off and set the cam right. Roll your chain in leaving the rockers off. You might want to remove the injectors so the engine will turn easier.
It is entirely possible that the injection pump timing has stayed correct versus the crank (as long as you do not confuse number 1 and number 4 cylinders (only the injection pump cares, the crank and cam don't). This is really important, remember it, if it don't start when its back together. You may be able to turn the cam 180 and have it be right. Let me know if you don't understand what I'm talking about here.
Bosch Master, ASE Master, L1
33 years MB technician