I know for certain that the IP of a 603.961 will work in a 603.971. The lifters too. And the camshaft. The IP seemed not to have the same pickup as the 603.971 pump, but actually made the car run much quieter and smoother. And for some reason, it seemed that the computer control functioned more precisely when the 603.961 pump was in the 3.5, i.e., the idle would raise up and settle back down, like on a gas powered car does, when the car is first started after sitting overnight.

The injectors would not fit in my car. The 3.5 injector threads are near the bottom of the injector body as opposed to the 3.0 threads being about a quarter of an inch higher toward the middle of the injector body, which made them not fit. Also, I believe the thread pitch is different, as well.

BenzDiesel