1million mile isx15 never been touched - what now?

[dccustomfarms]

I have just purchased a 15 model 389 Peterbilt with a million miles and 30k hours on the clock. Previous owner stated that the head, or the pan has never been off. I bought it knowing it was about do for rebuild. I have always had caterpillar engines. It's always been my practice to do rods and mains around every 300k mark. Are the red engines different? A million seems pretty far.

My question is, do I pull the pan and replace rod/main bearings? Inspect liners, and possibly change oil pump? Or do I go ahead and do complete in frame? Engine has good oil psi and very minimal blowby. Or should I run it a bit and see how it acts, and measure oil consumption? I do not want to do anything premature, but also don't want to take a chance of a rod destroying the block. From my research, a large percentage of these engines only make it to the 3-400k mark before failure. In this situation, what typically fails? Blown gaskets? Massive blow by and oil consumption? Or is it a ticking bomb wait to explode?

I do all of my own repairs and am not in hurry to put the truck on the road. Trying to decide the best approach for this situation. And also trying to learn the way of the red. Thanks for any and all input.