keep and fix it.
I agree with warwagon, nothing is truly reliable.
IMO reliability is just fixing what breaks before it breaks and leaves you stranded, or having a rig that will still get you home when multiple things go wrong, or having enough parts and tools on board to fix it, or any combination of those three. Each 6.5L of mine has a box of new parts it packs around and plenty of tools, and, cross fingers, I havent been stranded yet. just got back from a 3385 mile round trip in the 1650 dollar 95 6.5L (plus 400 dollar GMT800 alloys and tires, 400 dollar B&W turnover gooseneck ball, 300 dollar bilsteins, and a few oil changes and tags and ins., but still cheap auction bargain truck). lost boost on the return leg, and GP controller quit in wyoming, had to arc across with pliers to get GP's, but it made it.
On the trip, I saw many a new 100,000 dollar plus (heck, I think up to 150,000 dollar) new semi trucks dead on the side of the road from emissions shit breaking down. the less stuff to break, the less will break. dont forget the charred black top where alot of new rigs decide to catch fire. a local friend of a friend had an 07 jeep burn to the ground on the side of the freeway.
have you thought about a ted's motor to get going again, then tear down the other to figure out what went wrong? unfortunately it sounds like HG's or a crack are a strong possibility.
good luck in whatever you decide!