2005 5.9 Ram build.

Kinda like your hand there, if it ain't broke, don't fix it

380k miles is substantial for most engine, but a diesel?

Not unheard off

Plus, if the engine has 380k on it, I'm guessing 80% of the rest of the truck does too, so if you rebuild the engine, are you obliging yourself to replace everything else on it in the near future?
In fact I think I am willing to replace dang near everything on this truck.

I'm done with cars and car building for a while. (But I can't NOT have a project at home) this truck will be my new babby and I will tinker on it as time allows

I will say this is just about the worst case scenario. The Trans was brand new when the "engine" failed. My plan was to replace the engine and have a "new" truck.

Now I'm spending almost half the money and I still have a truck (engine) with 300+ thousand miles on it.

I'm to far gone to stop now tho so it just is what it is.