Well, I got the whole engine pulled today! Discovered something that has me worried -- The rad has a chunk of side tank missing at the bottom where the little round stud thing used to be, and there is was absolutely no coolant in the engine at all... I did run the engine like that, once for around 5 - 10 minutes

Should I be worried and pull the heads, or stab it in, and see what happens?

Other than that, no broken parts or wires anywhere, should be a pretty reasonably straight forward swap from here

Though, this does raise the question, do I find myself a new rad from another NBS truck, or can I somehow rig my old one in?