Originally Posted by Diseasel300

Yes, the IP will give the same power output regardless of whether you have it on a 603 or 606. The injection quantity is the same, so the power output will be the same. Horsepower increase comes from additional fuel and timing. The difference between the 3.0 and 3.4 pumps is largely in the torque capsule and RPM limiting. The 3.0 pump will pull hard to ~4600 RPM before tapering off fuel while the 3.4L pump will fall on its face ~4K with the 3.0L engine. It's just how they're tuned for the different displacements.

The bottom end on the 60x engines is extremely durable. If there's no noise or symptoms of wear, leave well enough alone.