If you have a W210 that has the 722.6 already installed.
If it is an OM606 with 722.6 Gearbox.
If you change Electric injection pump with OM603 pump, then the engine will run
There can be a problem if the Gearlever plug is removed from gear Lever that the car will not start. but
that can be handlet by leaving the originally plug in and not connect "OF Gear" Gearlever plug.
If it is an gasoline engine i6 or V8
If you change engine controller to aftermarked, do same way as abowe on the diesel.
If you want to use the originally engine controller.
Then try to remove big gearbox plug from gearbox
Start engine, put in D now you are in 2 gear and it will stay there.
Drive and test if engine has full power or in Limp home mode.
If no Limp mode try to remove gear Lever plug and see if engine can start ?
If it does not start put back the gear Lever plug, and just not connect "OF Gear" Gear Lever plug