Do I need an overhaul?

[Chamberpains]

If it hasn't been overhauled and I believe you said in your other post that the main bearings haven't been done, then you are absolutely driving a truck that will out of no where scatter the engine. It happened to my CM870 at 1.1 million with 15,000 lbs on the deck coasting down a slight hill. It started atop slightly knock and before I could get it pulled over to see what was happening, it sounded like someone threw gravel in the cylinders. I scattered cylinder #5. I was fortunate that it didn't blow a hole out the side of the block. So I was able to get the core value on the engine swap.