Ohcaptainron,

I agree with not replacing the engine (NOT MOTOR) until necessary. It may never fail. If it ain't broke, don't fix it.

But if you do replace the engine with a 300 SDL engine, I would put the 300SDL engine in as is and not change any parts especially the injection pump. All the parts are designed to work for the 3 liter engine. Maybe one of the parts you change is the part that makes the 3.5 liter engine fail.

P E H