One other thing to remember on cam timing. The crank has to turn two revolutions for every one revolution of the cam. The first lobe on the cam (closest to the chain) should be pointing up to the right, the second lobe on the cam should be pointing up and to the left. This is Cyl #1 on the top of its power stroke. You will have to remove the oil filter canister to remove the injection pump (Someone correct me if I'm wrong, but I've never been able to get the injection pump out of the way without moving that first).

1979 300D is 24 deg before top dead center on the injection pump timing. I'm pretty sure turbos are 25 degrees.